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  • Articles  (1,800)
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  • 1
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    Numerical Analysis of Copper-Indium-Gallium-Diselenide-Based Solar Cells by SCAPS-1D (2013)
    Hindawi
    Details
    Publication Date: 2013-09-11
    Description: We used a one-dimensional simulation program Solar Cell Capacitance Simulator in 1 Dimension (SCAPS-1D) to investigate Copper-Indium-Gallium-Diselenide- (CIGS-) based solar cells properties. Starting with a conventional ZnO-B/i-ZnO/CdS/CIGS structure, we simulated the parameters of current-voltage characteristics and showed how the absorber layer thickness, hole density, and band gap influence the short-circuit current density (), open-circuit voltage (), fill factor (FF), and efficiency of solar cell. Our simulation results showed that all electrical parameters are greatly affected by the absorber thickness (w) below 1000 nm, due to the increase of back-contact recombination and very poor absorption. Increasing hole density (p) or absorber band gap () improves and leads to high efficiency, which equals value of 16.1% when p = 1016 cm−3 and  eV. In order to reduce back-contact recombination, the effect of a very thin layer with high band gap inserted near the back contact and acting as electrons reflector, the so-called back-electron reflector (EBR), has been investigated. The performances of the solar cells are significantly improved, when ultrathin absorbers (w 〈 500 nm) are used; the corresponding gain of due to the EBR is 3 mA/cm2. Our results are in good agreement with those reported in the literature from experiments.
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  • 2
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    Solar Power Generation (2013)
    Hindawi
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    Publication Date: 2013-09-11
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  • 3
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    Effect of UV Irradiation on Interactions of -Lipoic Acid with Free Radicals (2013)
    Hindawi
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    Publication Date: 2013-09-12
    Description: Changes of antioxidant properties of -lipoic acid (LA) after UV irradiation were studied. LA is the typical drug used in diabetic neuropathy. Quenching of free radicals is an important factor of therapy by using this substance. -Lipoic acid is exposed to UV irradiation during the storage. The aim of our studies was to examine the effect of UV irradiation on the interactions of LA with free radicals. The -lipoic acid was irradiated by UVA 315–400 nm light during 10 to 110 minutes by intervals of 10 minutes. The electron paramagnetic resonance spectroscopy was used as the experimental technique. The antioxidant properties of LA were spectroscopically confirmed. The strong effect of UV irradiation on interactions of -lipoic acid with free radicals was observed. It was pointed out that interactions of LA with free radicals decrease after its exposition on UV. The interactions of LA with free radicals were higher after the sample irradiation during 10 minutes than for the samples irradiated longer (20–110 minutes). The results are important for problems connected with photomedicine; they pointed out that -lipoic acid should not be stored on UV exposition. Application of electron paramagnetic resonance spectroscopy to characterize interactions of pharmacological substance with free radicals was confirmed.
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  • 4
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    Enhanced Photoelectrochemical Response from Copper Antimony Zinc Sulfide Thin Films on Transparent Conducting Electrode (2013)
    Hindawi
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    Publication Date: 2013-09-12
    Description: Copper antimony sulfide (CAS) is a relatively new class of sustainable absorber material, utilizing cost effective and abundant elements. Band gap engineered, modified CAS thin films were synthesized using electrodeposition and elevated temperature sulfurization approach. A testing analog of copper zinc antimony sulfide (CZAS) film-electrolyte interface was created in order to evaluate photoelectrochemical performance of the thin film of absorber materials. Eu3+/Eu2+ redox couple was selected for this purpose, based on its relative band offset with copper antimony sulfide. It was observed that zinc has a significant effect on CAS film properties. An enhanced photocurrent was observed for CAS film, modified with zinc addition. A detailed investigation has been carried out by changing stoichiometry, and corresponding surface and optical characterization results have been evaluated. A summary of favorable processing parameters of the films showing enhanced photoelectrochemical response is presented.
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  • 5
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    - Calculations in CdS/CdTe Thin Films Solar Cells with a Interlayer (2013)
    Hindawi
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    Publication Date: 2013-09-12
    Description: In CdS/CdTe solar cells, chemical interdiffusion at the interface gives rise to the formation of an interlayer of the ternary compound . In this work, we evaluate the effects of this interlayer in CdS/CdTe photovoltaic cells in order to improve theoretical results describing experimental - (capacitance versus voltage) characteristics. We extended our previous theoretical methodology developed on the basis of three cardinal equations (Castillo-Alvarado et al., 2010). The present results provide a better fit to experimental data obtained from CdS/CdTe solar cells grown in our laboratory by the chemical bath deposition (for CdS film) and the close-spaced vapor transport (for CdTe film) techniques.
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  • 6
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    A Quantitative Analysis of Photovoltaic Modules Using Halved Cells (2013)
    Hindawi
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    Publication Date: 2013-09-12
    Description: In a silicon wafer-based photovoltaic (PV) module, significant power is lost due to current transport through the ribbons interconnecting neighbour cells. Using halved cells in PV modules is an effective method to reduce the resistive power loss which has already been applied by some major PV manufacturers (Mitsubishi, BP Solar) in their commercial available PV modules. As a consequence, quantitative analysis of PV modules using halved cells is needed. In this paper we investigate theoretically and experimentally the difference between modules made with halved and full-size solar cells. Theoretically, we find an improvement in fill factor of 1.8% absolute and output power of 90 mW for the halved cell minimodule. Experimentally, we find an improvement in fill factor of 1.3% absolute and output power of 60 mW for the halved cell module. Also, we investigate theoretically how this effect confers to the case of large-size modules. It is found that the performance increment of halved cell PV modules is even higher for high-efficiency solar cells. After that, the resistive loss of large-size modules with different interconnection schemes is analysed. Finally, factors influencing the performance and cost of industrial halved cell PV modules are discussed.
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  • 7
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    Research on the Comparison Analyses of Three-Phase Discrete and Integrated LC Filters in Three-Phase PV Inverter (2013)
    Hindawi
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    Publication Date: 2013-09-12
    Description: In three-phase photovoltaic (PV) system, three-phase filter inductors are important part for the output electrical power quality. The comparison analyses of three-phase discrete filter inductors and two kinds of three-phase integrated filter inductors in three-phase PV inverter are proposed. Firstly, the three-phase PV inverter operation with discrete filter inductors is analyzed, and the design of discrete filter inductors is given; then operation of the three-phase PV inverter with three-phase integrated five-limb magnetic core filter inductors is analyzed, the design of integrated filter inductors with five-limb magnetic core is given, then the operation of three-phase PV inverter with three-phase integrated three-limb magnetic core filter inductors is analyzed, and the design of integrated filter inductors with three limbs magnetic core is given. The conclusion of comparison between three-phase discrete filter inductors and two kinds of three-phase integrated filter inductors is done; it means that the three-phase discrete filter inductors can achieve better output electrical power quality with lower power density and three-phase integrated filter inductors can achieve higher power density with lower output electrical power quality. Finally, the experiment results are given to compare the volume and filter effect of three kinds of filter inductors in three-phase PV inverter.
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  • 8
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    Effectively Improved SiO2-TiO2 Composite Films Applied in Commercial Multicrystalline Silicon Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-09-13
    Description: Composite silicon dioxide-titanium dioxide (SiO2-TiO2) films are deposited on a large area of 15.6 × 15.6 cm2 textured multicrystalline silicon solar cells to increase the incident light trapped within the device. For further improvement of the antireflective coatings (ARCs) quality, dimethylformamide (DMF) solution is added to the original SiO2-TiO2 solutions. DMF solution solves the cracking problem, thus effectively decreasing reflectance as well as surface recombination. The ARCs prepared by sol-gel process and plasma-enhanced chemical vapor deposition (PECVD) on multicrystalline silicon substrate are compared. The average efficiency of the devices with improved sol-gel ARCs is 16.3%, only 0.5% lower than that of devices with PECVD ARCs (16.8%). However, from equipment depreciation point of view (the expiration date of equipment is generally considered as 5 years), the running cost (USD/watt) of sol-gel technique is 80% lower than that of PECVD method for the first five years and 66% lower than that of PECVD method from the start of the sixth year. This result proves that sol-gel-deposited ARCs process has potential applications in manufacturing low-cost, large-area solar cells.
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  • 9
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    Enhanced Solar Photoelectrochemical Conversion Efficiency of ZnO:Cu Electrodes for Water-Splitting Application (2013)
    Hindawi
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    Publication Date: 2013-09-20
    Description: n-type ZnO:Cu photoanodes were fabricated by simple spray pyrolysis deposition technique. Influence of low concentration (range ~10−4–10−1%) of Cu doping in hexagonal ZnO lattice on its photoelectrochemical performance has been investigated. The doped photoanodes displayed 7-time enhanced conversion efficiencies with respect to their undoped counterpart, as estimated from the photocurrents generated under simulated solar radiation. This is the highest enhancement in the solar conversion efficiency reported so far for the Cu-doped ZnO. This performance is attributed to the red shift in the band gap of the Cu-doped films and is in accordance with the incident-photon-current-conversion efficiency (IPCE) measurements. Electrochemical studies reveal an n-type nature of these photoanodes. Thus, the study indicates a high potential of doped ZnO films for solar energy applications, in purview of the development of simple nanostructuring methodologies.
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  • 10
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    Photovoltaic System Modeling with Fuzzy Logic Based Maximum Power Point Tracking Algorithm (2013)
    Hindawi
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    Publication Date: 2013-10-01
    Description: This paper represents a novel modeling technique of PV module with a fuzzy logic based MPPT algorithm and boost converter in Simulink environment. The prime contributions of this work are simplification of PV modeling technique and implementation of fuzzy based MPPT system to track maximum power efficiently. The main highlighted points of this paper are to demonstrate the precise control of the duty cycle with respect to various atmospheric conditions, illustration of PV characteristic curves, and operation analysis of the converter. The proposed system has been applied for three different PV modules SOLKAR 36 W, BP MSX 60 W, and KC85T 87 W. Finally the resultant data has been compared with the theoretical prediction and company specified value to ensure the validity of the system.
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  • 11
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    Preparation and Characterization of Chitosan Binder-Based Electrode for Dye-Sensitized Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-10-03
    Description: A chitosan binder-based TiO2 photoelectrode is used in dye-sensitized solar cells (DSSCs). Field-emission scanning electron microscope (FE-SEM) images revealed that the grain size, thickness, and distribution of TiO2 films are affected by the chitosan content. With addition of 2.0 wt% chitosan to the TiO2 film (D2), the surface pore size became the smallest, and the pores were fairly evenly distributed. The electron transit time, electron recombination lifetime, diffusion coefficient, and diffusion length were analyzed by IMVS and IMPS. The best DSSC, with 2.0 wt% chitosan addition to the TiO2 film, had a shorter electron transit time, longer electron recombination lifetime, and larger diffusion coefficient and diffusion length than the other samples. The results of 2.0 wt% chitosan-added TiO2 DSSCs are an electron transit time of  s, electron recombination lifetime of  s, diffusion coefficient of  cm2 s−1, diffusion length of 14.81 μm, and a solar conversion efficiency of 4.18%.
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  • 12
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    Synthesis of Nitrogen-Doped ZnS with Camellia Brushfield Yellow Nanostructures for Enhanced Photocatalytic Activity under Visible Light Irradiation (2013)
    Hindawi
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    Publication Date: 2013-10-03
    Description: Nitrogen modified zinc sulfide photocatalysts were successfully prepared and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and surface area analysis. Thermal decomposition of the semisolid was carried out under nitrogen conditions at 500°C for 2 hours, and a series of nitrogen-doped ZnS photocatalysts were produced by controlling inflow flow rate of nitrogen at 15–140 mL/min. Optical characterizations of the synthesized N-doping ZnS substantially show the shifted photoabsorption properties from ultraviolet (UV) region to visible light. The band gaps of nitrogen-doped ZnS composite catalysts were calculated to be in the range of 2.58~2.74 eV from the absorptions edge position. The 15N/ZnS catalyst shows the highest photocatalytic activity, which results in 75.7% degradation of Orange II dye in 5 hrs by visible light irradiation, compared with pristine ZnS and higher percentage N-doping ZnS photocatalysts.
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  • 13
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    DFT/TDDFT and Experimental Studies of Natural Pigments Extracted from Black Tea Waste for DSSC Application (2013)
    Hindawi
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    Publication Date: 2013-09-12
    Description: We report results of combined experimental and theoretical studies of black tea waste extract (BTE) as a potential sensitizer for TiO2-dye-sensitized solar cells (DSSCs). UV-vis absorption data revealed that BTE contains theaflavin. DSSC sensitized with pigment complexes of BTE showed a photon-energy conversion efficiency of %, while a significant increase (%) is observed when pH of the pigment solution was lowered. The HOMO and LUMO energy levels were calculated using experimental data of UV-vis absorption and cyclic voltammetry. These calculations revealed a reduction of the band gap by 0.17 eV and more negativity of HOMO level of acidified pigment, compared to that of original pigment. Combined effect of these developments caused the enhanced efficiency of DSSC. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) computational calculations were carried out to study the four theaflavin analogues which are responsible for the dark colour of BTE. According to the calculations, two theaflavin analogues, theaflavin and theaflavin digallate, are the most probable sensitizers in this dye-sensitized solar cell system.
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  • 14
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    Exergy, Energy, and Dynamic Parameter Analysis of Indigenously Developed Low-Concentration Photovoltaic System (2013)
    Hindawi
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    Publication Date: 2013-09-13
    Description: Piecewise linear parabolic trough collector (PLPTC) is designed and developed to concentrate solar radiation on monocrystalline silicon based photovoltaic module. A theoretical model is used to perform electrical energy and exergy analysis of low-concentration photovoltaic (LCPV) system working under actual test conditions (ATC). The exergy efficiency of LCPV system is in the range from 5.1% to 4.82% with increasing rate of input exergy rate from 30.81 W to 96.12 W, when concentration ratio changes from 1.85 to 5.17 Sun. Short-circuit current shows increasing trend with increasing input exergy rate of ≈0.011 A/W. Power conversion efficiency decreases from 7.07 to 5.66%, and open-circuit voltage decreases from 9.86 to 8.24 V with temperature coefficient of voltage  V/K under ATC. The results confirm that the commercially available silicon solar PV module performs satisfactorily under low concentration.
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  • 15
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    Optical and Electrical Properties of Thin Films of CuS Nanodisks Ensembles Annealed in a Vacuum and Their Photocatalytic Activity (2013)
    Hindawi
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    Publication Date: 2013-09-18
    Description: Effects on the optical, electrical, and photocatalytic properties of undoped CuS thin films nanodisks vacuum annealed at different temperatures were investigated. The chemical bath prepared CuS thin films were obtained at 40°C on glass substrates. The grain size of  nm was computed directly from high-resolution transmission electron microscopy (HRTEM) images. The electrical properties were measured by means of both Hall effect at room temperature and dark resistivity as a function of the absolute temperature 100–330 K. The activation energy values were calculated as 0.007, 0.013, and 0.013 eV for 100, 150, and 200°C, respectively. The energy band gap of the films varied in the range of 1.98 up to 2.34 eV. The photocatalytic activity of the CuS thin film was evaluated by employing the degradation of aqueous methylene blue solution in the presence of hydrogen peroxide. The CuS sample thin film annealed in vacuum at 150°C exhibited the highest photocatalytic activity in presence of hydrogen peroxide.
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  • 16
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    Radiation Effects in Solar Cells and Optoelectronic Devices (2013)
    Hindawi
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    Publication Date: 2013-09-20
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  • 17
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    Dye-Sensitized Solar Cell Based on Polyaniline/Multiwalled Carbon Nanotubes Counter Electrode (2013)
    Hindawi
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    Publication Date: 2013-09-30
    Description: This work presented the successful fabrication of dye-sensitized solar cell using polyaniline base (EB), multiwalled carbon nanotubes (MWCNTs), organic dye (rhodamine B or riboflavin), zinc oxide (ZnO), and indium tin oxide (ITO). The electrical properties of the resultant devices were investigated by measuring the current density voltage (-), capacitance voltage (-), and impedance measurements under both dark and illuminated conditions. The photovoltaic cell characteristics, that is, open circuit voltage (), short circuit current density (), and energy conversion efficiency (), were evaluated under illumination and were found to be 0.48 mA/cm2, 400 mV, and 0.224%, respectively, for ITO/EB-MWCNTs/ZnO-rhodamine B/ITO heterostructure. Using impedance spectra, it was found that the series resistances of this type of solar cell are 62 and 60 Ω under darkness and illumination, respectively.
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  • 18
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    Characterization of Natural Dye Extracted from Wormwood and Purple Cabbage for Dye-Sensitized Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-06-10
    Description: This study used natural dyes as sensitizers of dye-sensitized solar cells (DSSCs) to replace expensive chemical synthetic dyes. We prepared two natural dyes, chlorophyll dye and anthocyanin dye, by extracting them from wormwood and purple cabbage, respectively. Moreover, we mixed the prepared chlorophyll dye and anthocyanin dye at 5 different volume ratios to form cocktail dyes. For preparation of photoelectrode, P25 TiO2 nanoparticles were used to prepare paste, which was coated on fluorine-doped tin oxide (FTO) conductive glass by the spin coating method at different spin coating speeds in order to form TiO2 thin films with different thicknesses. The DSSC prepared by the cocktail dye achieves photoelectric conversion efficiency (η) of 1.95%, open-circuit voltage () of 0.765 V, and short-circuit current density () of 5.83 mA/cm2. Moreover, the prepared DSSC sensitized solely by chlorophyll extract of wormwood achieved a photoelectric conversion efficiency (η) of 0.9%, whereas the DSSC sensitized solely by anthocyanin extract of purple cabbage achieved a photoelectric conversion efficiency of 1.47%, achieving the longest lifetime of electrons amongst these three dyes.
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  • 19
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    Synthesis of Nanostructured Anatase Mesoporous Membranes with Photocatalytic and Separation Capabilities for Water Ultrafiltration Process (2013)
    Hindawi
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    Publication Date: 2013-03-22
    Description: In this work, the nanostructured anatase mesoporous membranes were prepared for water ultrafiltration (UF) process with photocatalytic and physical separation capabilities. A macroporous substrate was synthesized from α-Al2O3, then a colloidal titania sol was used for the preparation of the intermediate layer. Also, the membrane top layer was synthesized by deposition and calcination of titania polymeric sol on the intermediate layer. The characterization was performed by DLS, TG-DTA, XRD, BET, FESEM, TEM, and AFM techniques. Also, the filtration experiments were carried out based on separation of methyl orange from aqueous solution by a membrane setup with a dead-end filtration cell. Photocatalytic activity of the membranes was evaluated by methyl orange photodegradation using UV-visible spectrophotometer. The mean particle size of the colloidal and polymeric sols was 14 and 1.5 nm, respectively. The anatase membranes exhibited homogeneity, with the surface area of 32.8 m2/g, the mean pore size of 8.17 nm, and the crystallite size of 9.6 nm. The methyl orange removal efficiency by the mesoporous membrane based on physical separation was determined to be 52% that was improved up to 83% by a coupling photocatalytic technique. Thus, the UF membrane showed a high potential due to its multifunctional capability for water purification applications.
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  • 20
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    Optical and Electrical Properties of the Different Magnetron Sputter Power 300°C Deposited -ZnO Thin Films and Applications in p-i-n -Si:H Thin-Film Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-04-01
    Description: A compound of ZnO with 3 wt% Ga2O3 (ZnO : Ga2O3 = 97 : 3 in wt%, GZO) was sintered at C as a target. The GZO thin films were deposited on glass using a radio frequency magnetron sputtering system at C by changing the deposition power from 50 W to 150 W. The effects of deposition power on the crystallization size, lattice constant (c), resistivity, carrier concentration, carrier mobility, and optical transmission rate of the GZO thin films were studied. The blue shift in the transmission spectrum of the GZO thin films was found to change with the variations of the carrier concentration because of the Burstein-Moss shifting effect. The variations in the optical band gap () value of the GZO thin films were evaluated from the plots of , revealing that the measured value decreased with increasing deposition power. As compared with the results deposited at room temperature by Gong et al., (2010) the C deposited GZO thin films had apparent blue shift in the transmission spectrum and larger value. For the deposited GZO thin films, both the carrier concentration and mobility linearly decreased and the resistivity linearly increased with increasing deposition power. The prepared GZO thin films were also used as transparent electrodes to fabricate the amorphous silicon thin-film solar cells, and their properties were also measured.
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  • 21
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    Design and Manufacturing of a High-Precision Sun Tracking System Based on Image Processing (2013)
    Hindawi
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    Publication Date: 2013-09-06
    Description: Concentration solar arrays require greater solar tracking precision than conventional photovoltaic arrays. This paper presents a high precision low cost dual axis sun tracking system based on image processing for concentration photovoltaic applications. An imaging device is designed according to the principle of pinhole imaging, making sun rays to be received on a screen through pinhole and to be a sun spot. The location of the spot is used to adjust the orientation of the solar panel. A fuzzy logic controller is developed to achieve this goal. A prototype was built, and experimental results have proven the good performance of the proposed system and low error of tracking. The operation of this system is independent of geographical location, initial calibration, and periodical regulations.
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  • 22
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    Photostabilization of Phenoxyacetic Acid Herbicides MCPA and Mecoprop by Hydroxypropyl-β-cyclodextrin (2013)
    Hindawi
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    Publication Date: 2013-09-09
    Description: New strategies to reduce the environmental and economic costs of pesticides use are currently under study. Microencapsulation has been used as a versatile tool for the production of controlled release agricultural formulations. In this study, the photochemical degradation of the herbicides MCPA and mecoprop has been investigated in different aqueous media such as ultrapure and river water under simulated solar irradiation. To explore the possibility of introducing cyclodextrins in the herbicide formulations, the photodegradation study of the inclusion complexes of MCPA and mecoprop with (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was also performed. The half-lives of MCPA and mecoprop inclusion complexes were increased approximately by a factor of three related to the free molecules. Additionally, it has been shown that the photodegradation of MCPA and mecoprop is influenced by their structural features. The additional methyl group existing in mecoprop molecular structure has a positive influence on the stabilization of the radical intermediate formed in the first stage of photodegradation of both herbicides. The results found indicated that MCPA and mecoprop form inclusion complexes with HP-β-CD showing higher photostability compared to free herbicides indicating that HP-β-CD may serve as ingredient in these herbicide formulations.
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    Forecasting the Cell Temperature of PV Modules with an Adaptive System (2013)
    Hindawi
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    Publication Date: 2013-09-10
    Description: The need to reduce energy consumptions and to optimize the processes of energy production has pushed the technology towards the implementation of hybrid systems for combined production of electric and thermal energies. In particular, recent researches look with interest at the installation of hybrid system PV/T. To improve the energy performance of these systems, it is necessary to know the operating temperature of the photovoltaic modules. The determination of the operating temperature is a key parameter for the assessment of the actual performance of photovoltaic panels. In the literature, it is possible to find different correlations that evaluate the referring to standard test conditions and/or applying some theoretical simplifications/assumptions. Nevertheless, the application of these different correlations, for the same conditions, does not lead to unequivocal results. In this work an alternative method, based on the employment of artificial neural networks (ANNs), was proposed to predict the operating temperature of a PV module. This methodology does not require any simplification or physical assumptions. In the paper is described the ANN that obtained the best performance: a multilayer perception network. The results have been compared with experimental monitored data and with some of the most cited empirical correlations proposed by different authors.
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    Effect of Hydrogen Content in Intrinsic a-Si:H on Performances of Heterojunction Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-09-10
    Description: Influences of hydrogen content in intrinsic hydrogenated amorphous silicon (i-a-Si:H) on performances of heterojunction (HJ) solar cells are investigated. The simulation result shows that in the range of 0–18% of the i-layer hydrogen content, solar cells with higher i-layer hydrogen content can have higher degree of dangling bond passivation on single crystalline silicon (c-Si) surface. In addition, the experimental result shows that HJ solar cells with a low hydrogen content have a poor a-Si:H/c-Si interface. The deteriorate interface is assumed to be attributed to (i) voids created by insufficiently passivated c-Si surface dangling bonds, (ii) voids formed by SiH2 clusters, and (iii) Si particles caused by gas phase particle formation in silane plasma. The proposed assumption is well supported and explained from the plasma point of view using optical emission spectroscopy.
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    Multifunctional Chitosan-Copper Oxide Hybrid Material: Photocatalytic and Antibacterial Activities (2013)
    Hindawi
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    Publication Date: 2013-09-19
    Description: Chitosan (CS) anchored copper oxide (CuO) hybrid material was prepared by chemical precipitation method. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) confirmed the formation of CS-CuO hybrid. Transmission electron microscopy (TEM) analysis showed the immobilization of CuO nanoparticles on the surface of CS. The hybrid was also characterized by thermogravimetric analysis (TGA) and zeta potential. The hybrid exhibited high photocatalytic activity as evident from the degradation of methylene blue (MB) dye. The result revealed substantial degradation of the MB dye (84%) under UV-light illumination. The antibacterial activity of hybrid against Escherichia coli was examined by colony forming units. It was proved that the CS encapsulated CuO hybrid exhibited excellent antibacterial activity.
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    Thin Film CIGS Solar Cells, Photovoltaic Modules, and the Problems of Modeling (2013)
    Hindawi
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    Publication Date: 2013-09-19
    Description: Starting from the results regarding a nonvacuum technique to fabricate CIGS thin films for solar cells by means of single-step electrodeposition, we focus on the methodological problems of modeling at cell structure and photovoltaic module levels. As a matter of fact, electrodeposition is known as a practical alternative to costly vacuum-based technologies for semiconductor processing in the photovoltaic device sector, but it can lead to quite different structural and electrical properties. For this reason, a greater effort is required to ensure that the perspectives of the electrical engineer and the material scientist are given an opportunity for a closer comparison and a common language. Derived parameters from ongoing experiments have been used for simulation with the different approaches, in order to develop a set of tools which can be used to put together modeling both at single cell structure and complete module levels.
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    Dye-Sensitized Solar Cells: From Materials to Devices (2013)
    Hindawi
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    Publication Date: 2013-09-26
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    Green Synthesis of Feather-Shaped MoS2/CdS Photocatalyst for Effective Hydrogen Production (2013)
    Hindawi
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    Publication Date: 2013-09-27
    Description: MoS2/CdS photocatalyst was fabricated by a hydrothermal method for H2 production under visible light. This method used low toxic thiourea as a sulfur source and was carried out at 200°C. Thus, it was better than the traditional methods, which are based on an annealing process at relatively high temperature (above 400°C) using toxic H2S as reducing agent. Scanning electron microscopy and transmission electron microscopy images showed that the morphologies of MoS2/CdS samples were feather shaped and MoS2 layer was on the surface of CdS. The X-ray photoelectron spectroscopy testified that the sample was composed of stoichiometric MoS2 and CdS. The UV-vis diffuse reflectance spectra displayed that the loading of MoS2 can enhance the optical absorption of MoS2/CdS. The photocatalytic activity of MoS2/CdS was evaluated by producing hydrogen. The hydrogen production rate on MoS2/CdS reached 192 μmol·h−1. This performance was stable during three repeated photocatalytic processes.
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    A Cost-Effective Solid-State Approach to Synthesize g-C3N4 Coated TiO2 Nanocomposites with Enhanced Visible Light Photocatalytic Activity (2013)
    Hindawi
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    Publication Date: 2013-09-27
    Description: Novel graphitic carbon nitride (g-C3N4) coated TiO2 nanocomposites were prepared by a facile and cost-effective solid-state method by thermal treatment of the mixture of urea and commercial TiO2. Because the C3N4 was dispersed and coated on the TiO2 nanoparticles, the as-prepared g-C3N4/TiO2 nanocomposites showed enhanced absorption and photocatalytic properties in visible light region. The as-prepared g-C3N4 coated TiO2 nanocomposites under 450°C exhibited efficient visible light photocatalytic activity for degradation of aqueous MB due to the increased visible light absorption and enhanced MB adsorption. The g-C3N4 coated TiO2 nanocomposites would have wide applications in both environmental remediation and solar energy conversion.
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    Review of Polymer, Dye-Sensitized, and Hybrid Solar Cells (2014)
    Hindawi
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    Publication Date: 2014-12-15
    Description: The combination of inorganic nanoparticles semiconductor, conjugated polymer, and dye-sensitized in a layer of solar cell is now recognized as potential application in developing flexible, large area, and low cost photovoltaic devices. Several conjugated low bandgap polymers, dyes, and underlayer materials based on the previous studies are quoted in this paper, which can provide guidelines in designing low cost photovoltaic solar cells. All of these materials are designed to help harvest more sunlight in a wider range of the solar spectrum besides enhancing the rate of charge transfer in a device structure. This review focuses on developing solid-state dye-synthesized, polymer, and hybrid solar cells.
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    Near Infrared Radiation as a Rapid Heating Technique for TiO2 Films on Glass Mounted Dye-Sensitized Solar Cells (2014)
    Hindawi
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    Publication Date: 2014-11-07
    Description: Near infrared radiation (NIR) has been used to enable the sintering of TiO2 films on fluorine-doped tin oxide (FTO) glass in 12.5 s. The 9 µm thick TiO2 films were constructed into working electrodes for dye-sensitized solar cells (DSCs) achieving similar photovoltaic performance to TiO2 films prepared by heating for 30 min in a convection oven. The ability of the FTO glass to heat upon 12.5 s exposure of NIR radiation was measured using an IR camera and demonstrated a peak temperature of 680°C; glass without the 600 nm FTO layer reached 350°C under identical conditions. In a typical DSC heating step, a TiO2 based paste is heated until the polymeric binder is removed leaving a mesoporous film. The weight loss associated with this step, as measured using thermogravimetric analysis, has been used to assess the efficacy of the FTO glass to heat sufficiently. Heat induced interparticle connectivity in the TiO2 film has also been assessed using optoelectronic transient measurements that can identify electron lifetime through the TiO2 film. An NIR treated device produced in 12.5 seconds shows comparable binder removal, electron lifetime, and efficiency to a device manufactured over 30 minutes in a conventional oven.
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    Design of Multijunction Photovoltaic Cells Optimized for Varied Atmospheric Conditions (2014)
    Hindawi
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    Publication Date: 2014-11-07
    Description: Band gap engineering provides an opportunity to not only provide higher overall conversion efficiencies of the reference AM1.5 spectra but also customize PV device design for specific geographic locations and microenvironments based on atmospheric conditions characteristic to that particular location. Indium gallium nitride and other PV materials offer the opportunity for limited bandgap engineering to match spectra. The effects of atmospheric conditions such as aerosols, cloud cover, water vapor, and air mass have been shown to cause variations in spectral radiance that alters PV system performance due to both overrating and underrating. Designing PV devices optimized for spectral radiance of a particular region can result in improved PV system performance. This paper presents a new method for designing geographically optimized PV cells with using a numerical model for bandgap optimization. The geographic microclimate spectrally resolved solar flux for twelve representative atmospheric conditions for the incident radiation angle (zenith angle) of 48.1° and fixed array angle of 40° is used to iteratively optimize the band gap for tandem, triple, and quad-layer of InGaN-based multijunction cells. The results of this method are illustrated for the case study of solar farms in the New York region and discussed.
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    UV Blocking Glass: Low Cost Filters for Visible Light Photocatalytic Assessment (2014)
    Hindawi
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    Publication Date: 2014-12-09
    Description: A number of commercially available art protection products have been compared and assessed for their suitability as UV blocking filters in the application of “visible light” photocatalytic research. Many groups claiming visible light photocatalytic success employ filters to block out stray UV radiation in order to justify that their photocatalysts are indeed visible light photocatalysts and not UV light photocatalysts. These filters come in varying degrees of ability and price and many authors fail to correctly characterise their filters in individual papers. The use of effective filters to prevent both false positive and false negative results is important to maintain scientific rigor and create accurate understanding of the subject. The optimum UV filter would have the highest UV blocking properties (
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    Bottom-Up Enhancement of g-C3N4 Photocatalytic H2 Evolution Utilising Disordering Intermolecular Interactions of Precursor (2014)
    Hindawi
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    Publication Date: 2014-12-01
    Description: Disordered intermolecular interaction carbon nitride precursor prepared by water-assisted grinding of dicyandiamide was used for synthesis of g-C3N4. The final sample possesses much looser structure and provides a broadening optical window for effective light harvesting and charge separation efficiency, which exhibits significantly improved H2 evolution by photocatalytic water splitting. The bottom-up mechanochemistry method opens new vistas towards the potential applications of weak interactions in the photocatalysis field and may also stimulate novel ideas completely different from traditional ones for the design and optimization of photocatalysts.
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    Photocatalytic Water Splitting for Hydrogen Production with Novel M2YbSbO7 (M = In, Gd, Y) by Using Visible Light Photoenergy (2012)
    Hindawi
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    Publication Date: 2012-02-24
    Description: Novel photocatalysts M2YbSbO7 (M=In, Gd, Y) were synthesized by solid state reaction method for the first time. A comparative study on the structural and photocatalytic properties of M2YbSbO7 M2YbSbO7 (M=In, Gd, Y) was reported. The results showed that In2YbSbO7, Gd2YbSbO7, and Y2YbSbO7 crystallized with the pyrochlore-type structure, cubic crystal system and space group Fd3m. For the photocatalytic water splitting reaction, H2 or O2 evolution was observed from pure water with In2YbSbO7, Gd2YbSbO7, or Y2YbSbO7 as the photocatalyst under visible light irradiation. (wavelength>420 nm). Moreover, under visible light irradiation (λ>420 nm), H2 and O2 were also evolved by using In2YbSbO7, Gd2YbSbO7, or Y2YbSbO7 as catalyst from CH3OH/H2O and AgNO3/H2O solutions respectively. The In2YbSbO7 photocatalyst showed the highest activity compared with Gd2YbSbO7 or Y2YbSbO7. At the same time, The Y2YbSbO7 photocatalyst showed higher activity compared with Gd2YbSbO7. The photocatalytic activities were further improved under visible light irradiation with In2YbSbO7, Gd2YbSbO7, or Y2YbSbO7 being loaded by Pt, NiO, or RuO2. The effect of Pt was better than that of NiO or RuO2 for improving the photocatalytic activity of In2YbSbO7, Gd2YbSbO7, or Y2YbSbO7.
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    Eosin Yellowish Dye-Sensitized ZnO Nanostructure-Based Solar Cells Employing Solid PEO Redox Couple Electrolyte (2012)
    Hindawi
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    Publication Date: 2012-03-13
    Description: ZnO nanostructures are synthesized by low-temperature methods, and they possess polycrystalline hexagonal wurtzite structure with preferential c-axial growth. Morphological study by SEM shows the presence of ~30 nm sized spherical-shaped ZnO nanoparticle, the branched flower-like ZnO composed of many nanorods (length: 1.2 to 4.2 μm and diameter: 0.3 to 0.4 μm), and ~50 nm diameter of individual ZnO nanorods. Reduction in photoemission intensity of nanorods infers the decrease in electron-hole recombination rate, which offers better photovoltaic performance. The dye-sensitized solar cell (DSSC) based on ZnO nanorods sensitized with Eosin yellowish dye exhibits a maximum optimal energy conversion efficiency of 0.163% compared to that of nanoparticles and nanoflowers, due to better dye loading and direct conduction pathway for electron transport.
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    Benzothiazine Dyes/2,4,6-Tris(trichloromethyl)-1,3,5-triazine as a New Visible Two-Component Photoinitiator System (2012)
    Hindawi
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    Publication Date: 2012-12-25
    Description: Novel photoinitiator systems working under visible radiation were studied. The photoredox pair constructed with dye derivatives of 12H-quinoxalino-[2,3-b][1,4]-benzothiazine (1–3) and 2,4,6-tris(trichloromethyl)-1,3,5-triazine (Tz) were found to be effective initiators for free radical polymerization of trimethylolpropane triacrylate (TMPTA) using VIS light. Photosensitization occurred through electron transfer, which was confirmed by the observation of a radical cation of the studied dyes. The 1•+ was also characterized in cryogenic matrices (mixture of CH2Cl2 and ionic liquid: 1-butyl-3-methylimidazolium hexafluorophosphate ( −)) and its reactivity was investigated by means of pulse radiolysis in solution at room temperature. In a halogenated solvent and in a mixture of CH2Cl2 and  −, the radical cation 1•+ underwent deprotonation to form a neutral radical 1•, which was stable in the second time scale. During photolysis of the 1/Tz photoredox pair in 1-methyl-2-pyrrolidone and monomer, the formation of a neutral radical 1• was not observed.
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    First-Principles Study on Influences of Crystal Structure and Orientation on Band Offsets at the CdS/Cu2ZnSnS4 Interface (2013)
    Hindawi
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    Publication Date: 2013-01-02
    Description: Cu2ZnSnS4 (CZTS) has attracted much attention recently as an absorber layer material in a heterojunction solar cell. Using the first-principles method, we calculate the band offsets for the CdS/CZTS heterojunction. The valence band offset is 1.2 eV for the (001) CdS/CZTS heterointerface and 1.0 eV for the (010) heterointerface, when CZTS is considered to crystallize in the kesterite structure. When CZTS is considered to crystallize in the stannite structure,  eV for the (001) heterointerface and  eV for the (010) heterointerface. In any case, the conduction band minimum of CZTS is higher than that of CdS, and the conduction band offset is in a range between 0.1 and 0.4 eV.
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    The Comparison of Photocatalytic Degradation and Decolorization Processes of Dyeing Effluents (2013)
    Hindawi
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    Publication Date: 2013-02-21
    Description: Treatment of dye effluents resulting from the industrial scale dyeing of cotton, polyacrylic fibres, leather, and flax fabrics by photocatalytic methods was investigated. Photocatalytic processes were initiated by UV-a light ( 366 nm) and were conducted in the presence of TiO2, TiO2/FeCl3, or FeCl3 as photocatalysts. It was found that the photocatalytic process carried out with TiO2 and TiO2/FeCl3 was the most effective method for decolorization of textile dyeing effluents and degradation of dyes, except for effluents containing very high concentrations of stable azo dyes. During the photocatalytic degradation of anionic dyes, a mixture of TiO2/FeCl3 was more effective, while in the case of cationic dyes, more suitable seems to be TiO2 alone.
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    Reliable and Damage-Free Estimation of Resistivity of ZnO Thin Films for Photovoltaic Applications Using Photoluminescence Technique (2013)
    Hindawi
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    Publication Date: 2013-02-21
    Description: This work projects photoluminescence (PL) as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO) thin films. ZnO thin films, deposited using chemical spray pyrolysis (CSP) by varying the deposition parameters like solvent, spray rate, pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the luminescence properties as well as resistivity. Two emissions could be recorded for all samples—the near band edge emission (NBE) at 380 nm and the deep level emission (DLE) at ~500 nm which are competing in nature. It is observed that the ratio of intensities of DLE to NBE (/) can be reduced by controlling oxygen incorporation in the sample. - measurements indicate that restricting oxygen incorporation reduces resistivity considerably. Variation of / and resistivity for samples prepared under different deposition conditions is similar in nature. / was always less than resistivity by an order for all samples. Thus from PL measurements alone, the order of resistivity of the samples can be estimated.
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    Tailoring the Spectra of White Organic Light-Emitting Devices by Trap Effect of a Concentration-Insensitive Dopant (2013)
    Hindawi
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    Publication Date: 2013-02-21
    Description: Highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by using a novel iridium complex, bis[2-(,-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,]iridium(III) (acetylacetonate) [(tbpbt)2Ir(acac)], as the emitter. With a wide doping ratio ranging from 15 wt% to 25 wt%, the PhOLEDs maintained a comparable high performance, indicating concentration-insensitive property of the (tbpbt)2Ir(acac). On the basis of the unique characteristic of concentration insensitivity, the application of this phosphor was explored by fabricating white organic light-emitting devices (WOLEDs) with altered doping ratio, indicating that trap effect of (tbpbt)2Ir(acac) could effectively tailor WOLEDs spectra. Typically, a high-power efficiency, current efficiency, and external quantum efficiency of 30.0 lm/W, 38.8 cd/A, 18.1%, were achieved by 20 wt% doped WOLEDs.
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    Preparation of Improved p-n Junction NiO/TiO2 Nanotubes for Solar-Energy-Driven Light Photocatalysis (2013)
    Hindawi
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    Publication Date: 2013-02-21
    Description: Self-organized TiO2 nanotubes (TNTs) with average inner diameter of 109 nm, wall thickness of 15 nm, and tube length of 7–10 μm were loaded with nickel oxide (NiO) nanoparticles via incipient wet impregnation method. The molar concentration of Ni(NO3)2·6H2O aqueous solution varied in a range of 0.5 M–2.5 M. The samples were characterized for crystalline phase, morphology, topography, chemical composition, Raman shift, and UV-Vis diffusion reflection properties. The finding shows that the loading of NiO did not influence the morphology, structure, and crystalline phase of TNTs but it exhibited significant effect on crystallite size and optical absorption properties. Further, the solar-energy-driven the photocatalytic activity of NiO/TNTs and pure TNTs was evaluated by degrading methylene blue (MB). The results confirm that photocatalytic efficiency of NiO/TNTs is higher than that of TNTs.
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    Synthesis, Characterization, and Photocatalytic Activity of N-Doped ZnO/ZnS Composites (2013)
    Hindawi
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    Publication Date: 2013-02-21
    Description: The aim of the present study is to enhance photocatalytic performance of ZnO semiconductor by comodification with doping of nonmetal ions and coupling with another semiconductor. Therefore, we synthesized the N-doped ZnO/ZnS photocatalysts via a simple heat-treatment approach using L-cysteine as N and S source in this work. Anthraquinone dye (reactive brilliant blue KNR) is employed as the model contaminants to evaluate the photocatalytic activity of as-synthesized samples under sunlight illumination. The N-doped ZnO/ZnS synthesized by this method shows better photocatalytic activity as compared to that of pure ZnO. The enhanced photocatalytic activity of the N-doped ZnO/ZnS composites may be related to the existence of N doping, ZnS/ZnO heterostructure, and covered abundant carbon species on the photocatalyst surface, which causing high absorption efficiency of light, efficient separation of electron-hole pairs, and quick surface reaction in doped ZnO.
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    Mechanisms of Visible Light Photocatalysis in N-Doped Anatase TiO2 with Oxygen Vacancies from GGA+U Calculations (2013)
    Hindawi
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    Publication Date: 2013-02-21
    Description: We have systematically studied the photocatalytic mechanisms of nitrogen doping in anatase TiO2 using first-principles calculations based on density functional theory, employing Hubbard U (8.47 eV) on-site correction. The impurity formation energy, charge density, and electronic structure properties of TiO2 supercells containing substitutional nitrogen, interstitial nitrogen, or oxygen vacancies were evaluated to clarify the mechanisms under visible light. According to the formation energy, a substitutional N atom is better formed than an interstitial N atom, and the formation of an oxygen vacancy in N-doped TiO2 is easier than that in pure TiO2. The calculated results have shown that a significant band gap narrowing may only occur in heavy nitrogen doping. With light nitrogen doping, the photocatalysis under visible light relies on N-isolated impurity states. Oxygen vacancies existence in N-doped TiO2 can improve the photocatalysis in visible light because of a band gap narrowing and n-type donor states. These findings provide a reasonable explanation of the mechanisms of visible light photocatalysis in N-doped TiO2.
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    H2O2 Treatment of Electrochemically Deposited Cu2O Thin Films for Enhancing Optical Absorption (2013)
    Hindawi
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    Publication Date: 2013-02-22
    Description: Cu2O is considered to be promising as an absorber layer material of solar cells, but its band gap (about 2.1 eV) is larger than the optimum one (about 1.5 eV). CuO has a smaller band gap of about 1.35 eV. Therefore, we attempted to oxidize Cu2O using H2O2 to increase oxygen ratio and decrease band gap. Cu2O thin films were deposited on indium-tin-oxide-coated glass from an aqueous solution containing CuSO4, lactic acid, and KOH by the galvanostatic electrochemical deposition at 40°C with current density of −1 mA/cm2. Then, the as-prepared copper oxide thin film was dipped in H2O2 (30%) at fixed temperature to oxidize for some time. By the H2O2 treatment at room temperature, the oxygen content was increased, and the band gap was decreased.
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    Preparation of N- Using a Microwave/Sol-Gel Method and Its Photocatalytic Activity for Bisphenol A under Visible-Light and Sunlight Irradiation (2013)
    Hindawi
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    Publication Date: 2013-02-25
    Description: This study applied the microwave/sol-gel method to prepare nitrogen-doped TiO2 (N-TiO2). The N-TiO2 was immobilized in glass balls to form N-TiO2/glass beads and applied to degrade Bisphenol A (BPA) under visible-light and sunlight irradiation. The characteristics of the prepared photocatalysts were analyzed by X-ray diffraction (XRD), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Experimental results demonstrate that the percentage of anatase increased as the amount of N in N-TiO2 increased. Compared with the undoped TiO2 (420 nm), spectra show that the absorption edge shifted to a longer wavelength (445 nm) after N doping. The XPS characterization confirms the substitution of crystal lattice O to N species in N-TiO2, forming Ti–O–N and N–Ti–O. With an increased N/Ti ratio, photodegradation efficiency increased and then decreased; moreover, the optimal amount for N doping was determined as an N/Ti mole ratio of 0.08 (0.1 NT). The efficiency of 0.1 NT in doing BPA photodegradation was greater than that of Degussa P25. After reaction for 61 min, the mineralization percentage of 0.1 NT under visible-light irradiation reached 41%. Photocatalyst efficiency decreased as the number of repeats increased in the visible-light/N-TiO2 system; however, these systems were stable during reaction.
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    Facile Growth of Porous Hematite Films for Photoelectrochemical Water Splitting (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: We introduced a simple fabrication method of porous hematite films with tunable thickness in an aqueous solution containing FeCl3 as the single precursor. We demonstrated that the optimized thickness was necessary for high performance photoelectrochemical water splitting, by balancing photon absorption and charge carrier transport. The highest photocurrent of ca. 0.15 mA cm−2 at 1.0 V versus Ag/AgCl was achieved on the 300 nm thick porous hematite film as photoanode, with IPCE at 370 nm and 0.65 V versus Ag/AgCl to be 9.0%. This simple method allows the facile fabrication of hematite films with porous nanostructure for enabling high photon harvesting efficiency and maximized interfacial charge transfer. These porous hematite films fabricated by this simple solution-based method could be easily modified by metal doping for further enhanced photoelectrochemical activity for water splitting.
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    Applying a Cerebellar Model Articulation Controller Neural Network to a Photovoltaic Power Generation System Fault Diagnosis (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: This study employed a cerebellar model articulation controller (CMAC) neural network to conduct fault diagnoses on photovoltaic power generation systems. We composed a module array using 9 series and 2 parallel connections of SHARP NT-R5E3E 175 W photovoltaic modules. In addition, we used data that were outputted under various fault conditions as the training samples for the CMAC and used this model to conduct the module array fault diagnosis after completing the training. The results of the training process and simulations indicate that the method proposed in this study requires fewer number of training times compared to other methods. In addition to significantly increasing the accuracy rate of the fault diagnosis, this model features a short training duration because the training process only tunes the weights of the exited memory addresses. Therefore, the fault diagnosis is rapid, and the detection tolerance of the diagnosis system is enhanced.
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    Fabrication of a Cu(InGa)Se2 Thin Film Photovoltaic Absorber by Rapid Thermal Annealing of CuGa/In Precursors Coated with a Se Layer (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: Cu(InGa)Se2 (CIGS) thin film absorbers are prepared using sputtering and selenization processes. The CuGa/In precursors are selenized during rapid thermal annealing (RTA), by the deposition of a Se layer on them. This work investigates the effect of the Cu content in precursors on the structural and electrical properties of the absorber. Using X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, and Hall effect measurement, it is found that the CIGS thin films produced exhibit facetted grains and a single chalcopyrite phase with a preferred orientation along the (1 1 2) plane. A Cu-poor precursor with a Cu/() ratio of 0.75 demonstrates a higher resistance, due to an increase in the grain boundary scattering and a reduced carrier lifetime. A Cu-rich precursor with a Cu/() ratio of 1.15 exhibits an inappropriate second phase () in the absorber. However, the precursor with a Cu/() ratio of 0.95 exhibits larger grains and lower resistance, which is suitable for its application to solar cells. The deposition of this precursor on Mo-coated soda lime glass substrate and further RTA causes the formation of a MoSe2 layer at the interface of the Mo and CIGS.
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    TiO2 and ZnO Nanoparticles in Photocatalytic and Hygienic Coatings (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: Antimicrobial paints were based on the aqueous acrylic dispersion and various nanoparticles of zinc oxide and titanium dioxide. Antimicrobial ability and photoactivity were assumed in these paints. It was possible to observe the photoactivity thanks to change of organic dyes due to oxidative-reductive reaction. The best photocatalytic effect showed the coating containing the mixture of the first type of TiO2 and nano-ZnO despite the fact that the first type of TiO2 was not better in the photocatalytic test than the other types of TiO2. The agar dilution method was used to test antimicrobial ability. The Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were chosen as test bacteria and Penicillium chrysogenum and Aspergillus niger as test molds. The antimicrobial effect of coatings with the mixture of the first type of TiO2 and nano-ZnO was the best of all the tested samples.
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    Reduction of Oxygen Impurity in Multicrystalline Silicon Production (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: Effective control of oxygen impurity in multicrystalline silicon is required for the production of a high-quality crystal. The basic principle and some techniques for reducing oxygen impurity in multicrystalline silicon during the unidirectional solidification process are described in this paper. The oxygen impurity in multicrystalline silicon mainly originates from the silica crucible. To effectively reduce the oxygen impurity, it is essential to reduce the oxygen generation and enhance oxygen evaporation. For reduction of oxygen generation, it is necessary to prevent or weaken any chemical reaction with the crucible, and for the enhancement of oxygen evaporation, it is necessary to control convection direction of the melt and strengthen gas flow above the melt. Global numerical simulation, which includes heat transfer in global furnace, argon gas convection inside furnace, and impurity transport in both melt and gas regions, has been implemented to validate the above methods.
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    Key Success Factors and Future Perspective of Silicon-Based Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: Today, after more than 70 years of continued progress on silicon technology, about 85% of cumulative installed photovolatic (PV) modules are based on crystalline silicon (c-Si). PV devices based on silicon are the most common solar cells currently being produced, and it is mainly due to silicon technology that the PV has grown by 40% per year over the last decade. An additional step in the silicon solar cell development is ongoing, and it is related to a further efficiency improvement through defect control, device optimization, surface modification, and nanotechnology approaches. This paper attempts to briefly review the most important advances and current technologies used to produce crystalline silicon solar devices and in the meantime the most challenging and promising strategies acting to increase the efficiency to cost/ratio of silicon solar cells. Eventually, the impact and the potentiality of using a nanotechnology approach in a silicon-based solar cell are also described.
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    Experimental Investigation on an Absorption Refrigerator Driven by Solar Cells (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: This experiment is to study an absorption refrigerator driven by solar cells. Hand-held or carried in vehicle can be powered by solar energy in places without power. In the evenings or rainy days, it is powered by storage battery, and it can be directly powered by alternating current (AC) power supply if available, and the storage battery can be charged full as a backup supply. The proposed system was tested by the alternation of solar irradiance 550 to 700 W/m2 as solar energy and 500ml ambient temperature water as cooling load. After 160 minutes, the proposal refrigerator can maintain the temperature at 5–8°C, and the coefficient of performance (COP) of NH3-H2O absorption refrigeration system is about 0.25. Therefore, this system can be expected to be used in remote areas for refrigeration of food and beverages in outdoor activities in remote and desert areas or long-distance road transportation of food or low temperature refrigeration of vaccine to avoid the deterioration of the food or the vaccines.
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    Effect of Annealing Temperature on CuInSe2/ZnS Thin-Film Solar Cells Fabricated by Using Electron Beam Evaporation (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: CuInSe2 (CIS) thin films are successfully prepared by electron beam evaporation. Pure Cu, In, and Se powders were mixed and ground in a grinder and made into a pellet. The pallets were deposited via electron beam evaporation on FTO substrates and were varied by varying the annealing temperatures, at room temperature, 250°C, 300°C, and 350°C. Samples were analysed by X-ray diffractometry (XRD) for crystallinity and field-emission scanning electron microscopy (FESEM) for grain size and thickness. I-V measurements were used to measure the efficiency of the CuInSe2/ZnS solar cells. XRD results show that the crystallinity of the films improved as the temperature was increased. The temperature dependence of crystallinity indicates polycrystalline behaviour in the CuInSe2 films with (1 1 1), (2 2 0)/(2 0 4), and (3 1 2)/(1 1 6) planes at 27°, 45°, and 53°, respectively. FESEM images show the homogeneity of the CuInSe2 formed. I-V measurements indicated that higher annealing temperatures increase the efficiency of CuInSe2 solar cells from approximately 0.99% for the as-deposited films to 1.12% for the annealed films. Hence, we can conclude that the overall cell performance is strongly dependent on the annealing temperature.
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    RF Magnetron Sputtering Aluminum Oxide Film for Surface Passivation on Crystalline Silicon Wafers (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: Aluminum oxide films were deposited on crystalline silicon substrates by reactive RF magnetron sputtering. The influences of the deposition parameters on the surface passivation, surface damage, optical properties, and composition of the films have been investigated. It is found that proper sputtering power and uniform magnetic field reduced the surface damage from the high-energy ion bombardment to the silicon wafers during the process and consequently decreased the interface trap density, resulting in the good surface passivation; relatively high refractive index of aluminum oxide film is benefic to improve the surface passivation. The negative-charged aluminum oxide film was then successfully prepared. The surface passivation performance was further improved after postannealing by formation of an SiOx interfacial layer. It is demonstrated that the reactive sputtering is an effective technique of fabricating aluminum oxide surface passivation film for low-cost high-efficiency crystalline silicon solar cells.
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    Competing in the Global Solar Photovoltaic Industry: The Case of Taiwan (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: The top five solar cell supply countries in the world in sequential order are China, Taiwan, the United States of America, Japan, and Germany. The capacity of Taiwanese solar cell production is ranked top two in the globe. The competitive advantage of the Taiwanese electronics firms has facilitated the rapid developments to its solar photovoltaic industry. The Taiwanese solar photovoltaic industry possesses a large size and a complete value chain of upstream, midstream, and downstream sectors. In this study, I analyzed the trends and developments of the solar photovoltaic industry in Taiwan and in the globe. And I also investigated the positioning and competitive advantage of Taiwanese firms in the value chain of the global solar photovoltaic industry. I found that Taiwanese firms continue to have an important and indispensable role in the global solar photovoltaic industry by either differentiation or cost advantage.
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    Release of Volatile Compounds from Polymeric Microcapsules Mediated by Photocatalytic Nanoparticles (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: In this study we propose a suitable method for the solar-activated controlled release of volatile compounds from polymeric microcapsules bonded with photocatalytic nanoparticles. These reservoirs can find applications, for example, in the controlled release of insecticides, repellents, or fragrances, amongst other substances. The surfaces of the microcapsules have been functionalized with TiO2 nanoparticles. Upon ultraviolet irradiation, redox mechanisms are initiated on the semiconductor surface resulting in the dissociation of the polymer chains of the capsule wall and, finally, volatilization of the encapsulated compounds. The quantification of the output release has been performed by gas chromatography analysis coupled with mass spectroscopy.
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    Effect of PdS on Photocatalytic Hydrogen Evolution of Nanostructured CdS under Visible Light Irradiation (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: To investigate the effect of PdS as a cocatalyst for photocatalytic hydrogen evolution, nanostructured PdS/CdS were prepared by an in situ coprecipitation and hydrothermal method, respectively. The as-prepared photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-visible absorption spectra, and photoluminescence spectra (PL). With PdS highly dispersed in the CdS nanostructures, the photoactivity was evaluated by hydrogen evolution from aqueous solution containing Na2S/Na2SO3 as sacrificial reagents under visible light irradiation. When the concentration of PdS was 1% by weight, PdS/CdS, prepared by the in situ coprecipitation, showed the highest photocatalytic activity, while that prepared by hydrothermal method showed the most stability for hydrogen evolution. The effect of highly dispersed PdS on the photoactivity was discussed.
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    The Evaluation of Solar Contribution in Solar Aided Coal-Fired Power Plant (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: Solar aided coal-fired power plants utilize various types of solar thermal energy for coupling coal-fired power plants by using the characteristics of various thermal needs of the plants. In this way, the costly thermal storage system and power generating system will be unnecessary while the intermittent and unsteady way of power generation will be avoided. Moreover, the large-scale utilization of solar thermal power and the energy-saving aim of power plants will be realized. The contribution evaluating system of solar thermal power needs to be explored. This paper deals with the evaluation method of solar contribution based on the second law of thermodynamics and the principle of thermoeconomics with a case of 600 MW solar aided coal-fired power plant. In this study, the feasibility of the method has been carried out. The contribution of this paper is not only to determine the proportion of solar energy in overall electric power, but also to assign the individual cost components involving solar energy. Therefore, this study will supply the theoretical reference for the future research of evaluation methods and new energy resource subsidy.
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    Low-Voltage Ride-Through Capability of a Single-Stage Single-Phase Photovoltaic System Connected to the Low-Voltage Grid (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: The progressive growing of single-phase photovoltaic (PV) systems makes the Distribution System Operators (DSOs) update or revise the existing grid codes in order to guarantee the availability, quality, and reliability of the electrical system. It is expected that the future PV systems connected to the low-voltage grid will be more active with functionalities of low-voltage ride-through (LVRT) and the grid support capability, which is not the case today. In this paper, the operation principle is demonstrated for a single-phase grid-connected PV system in a low-voltage ride-through operation in order to map future challenges. The system is verified by simulations and experiments. Test results show that the proposed power control method is effective and the single-phase PV inverters connected to low-voltage networks are ready to provide grid support and ride-through voltage fault capability with a satisfactory performance based on the grid requirements for three-phase renewable energy systems.
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    Advanced Oxidation Processes for Wastewater Treatment (2013)
    Hindawi
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    Publication Date: 2013-03-07
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    Silver Nanoparticle-Doped Titanium Oxide Thin Films for Intermediate Layers in Organic Tandem Solar Cell (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: In this work we investigate the Ag nanoparticle doping of TiOx used as an intermediate layer between subcells of a tandem organic photovoltaic. We use a model polymer cell structure of P3HT:TiOx:PEDOT:P3HT to observe charge-trapping effects as a function of nanoparticle content in the TiOx, as determined by the shape of the dark and illuminated current voltage curves of the devices. There is a direct correlation between the amount of Ag nanoparticles in the TiOx, and interfacial charge buildup, and charge trapping being completely mitigated at around 0.2% mol. This suggests that such doping schemes might provide a simple approach to the creation and use of TiOx layers for tandem cells.
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    Development of a Wind Directly Forced Heat Pump and Its Efficiency Analysis (2013)
    Hindawi
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    Publication Date: 2013-03-07
    Description: The requirements of providing electric energy through the wind-forced generator to the heat pump for water cooling and hot water heating grow significantly by now. This study proposes a new technique to directly adopt the wind force to drive heat pump systems, which can effectively reduce the energy conversion losses during the processes of wind force energy converting to electric energy and electric energy converting to kinetic energy. The operation of heat pump system transfers between chiller and heat that are controlled by a four-way valve. The theoretical efficiency of the traditional method, whose heat pump is directly forced by wind, is 42.19%. The experimental results indicated average value for cool water producing efficiency of 54.38% in the outdoor temperature of 35°C and the indoor temperature of 25°C and the hot water producing efficiency of 52.25% in the outdoor temperature and the indoor temperature both of 10°C. We proposed a method which can improve the efficiency over 10% in both cooling and heating.
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    Metallisation and Interconnection of e-Beam Evaporated Polycrystalline Silicon Thin-Film Solar Cells on Glass (2012)
    Hindawi
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    Publication Date: 2012-10-12
    Description: One inherent advantage of thin-film technology is the possibility of using monolithic integration for series interconnection of individual cells within large-area modules. Polycrystalline silicon thin-film solar cells do not rely on transparent conducting oxide layers as the high sheet conductivity of the emitter and BSF layers enables the lateral flow of current from the film to the metal contacts. This paper presents a new method for the fabrication of e-beam evaporated polycrystalline thin-film photovoltaic minimodules on glass. The method involves electrically isolating minicells, by laser scribing, and then forming an isolation layer on each laser scribe. The main advantage of this metallisation is to have a single aluminium evaporation step for the formation of finger and busbar features, as well as for series interconnection.
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    A Study on the Working Performance of Dimming Methods for Single- and Multichip Power LEDs (2012)
    Hindawi
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    Publication Date: 2012-10-25
    Description: Light emitting diodes (LEDs) have many positive features, such as long life, low power consumption, and high luminous efficacy. Consequently, they are very attractive for use in many applications. Also, the use of LEDs ensures energy savings. Power LEDs have increasingly been used for general lighting via multichip module technology. The output of power LEDs should be controlled to obtain life and illuminance values in catalog. In this study, the effects of different dimming methods are investigated for single-and multichip LEDs. To achieve this aim, pulse width modulation (PWM) and current variation (CV) dimming methods are applied to single and multichip power LEDs during ten stages of dimming. A current-regulated DC source is used for current variation (CV) dimming, and a driver designed by the researcher is used for pulse width modulation (PWM) dimming. Moreover, all of the applications are made for active and passive cooling. Finally, the results are compared.
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    Microcrystalline-Silicon-Oxide-Based N-Type Reflector Structure in Micromorph Tandem Solar Cells (2012)
    Hindawi
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    Publication Date: 2012-04-09
    Description: N-type microcrystalline silicon oxide thin films (n-μc-SiOx:H) have been deposited by VHF-PECVD (40 MHz) with reactant gas mixtures of CO2/SiH4 and H2. N-μc-SiOx thin films exhibiting low refractive index value (n600 nm~2), and medium/high conductivity (≧10-9 S/cm) are suitable to be used as an “n-type reflector” in micromorph tandem solar cells. Transmission electron microscopy (TEM) results show that microstructures of n-μc-SiOx:H thin films contain nanocrystalline Si particles, which are randomly embedded in the a-SiOx matrix. This specific microstructure provides n-μc-SiOx:H thin films excellent optoelectronic properties; therefore, n-μc-SiOx:H thin films are appropriate candidates for “n-type reflector” structures in Si tandem solar cells.
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    UV Filtering of Dye-Sensitized Solar Cells: The Effects of Varying the UV Cut-Off upon Cell Performance and Incident Photon-to-Electron Conversion Efficiency (2012)
    Hindawi
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    Publication Date: 2012-04-09
    Description: With current technology, UV filters are essential to ensure long-term dye-sensitized solar cell (DSC) stability. Blocking photons, however, will have an obvious effect on device performance and upon its incident photon-to-current conversion efficiency (IPCE). Filters have been applied to DSC devices with a range of cut-off wavelengths in order to assess how different levels of filtering affect the performance and IPCE of devices made with three different dyes, namely N719, Z907, and N749. It is shown that dyes that extend their IPCE further into the NIR region suffer lesser relative efficiency losses due to UV filtering than dyes with narrower action spectra. Furthermore, the results are encouraging to those working towards the industrialisation of DSC technology. From the results presented it can be estimated that filtering at a level intended to prevent direct band gap excitation of the TiO2 semiconductor should cause a relative drop in cell efficiency of no more than 10% in forward illuminated devices and no more than 2% in reverse illuminated devices.
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    Preparation of Improved p-n Junction NiO/TiO2 Nanotubes for Solar-Energy-Driven Light Photocatalysis (2013)
    Hindawi
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    Publication Date: 2013-02-08
    Description: Self-organized TiO2 nanotubes (TNTs) with average inner diameter of 109 nm, wall thickness of 15 nm, and tube length of 7–10 μm were loaded with nickel oxide (NiO) nanoparticles via incipient wet impregnation method. The molar concentration of Ni(NO3)2·6H2O aqueous solution varied in a range of 0.5 M–2.5 M. The samples were characterized for crystalline phase, morphology, topography, chemical composition, Raman shift, and UV-Vis diffusion reflection properties. The finding shows that the loading of NiO did not influence the morphology, structure, and crystalline phase of TNTs but it exhibited significant effect on crystallite size and optical absorption properties. Further, the solar-energy-driven the photocatalytic activity of NiO/TNTs and pure TNTs was evaluated by degrading methylene blue (MB). The results confirm that photocatalytic efficiency of NiO/TNTs is higher than that of TNTs.
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    Mechanisms of Visible Light Photocatalysis in N-Doped Anatase TiO2 with Oxygen Vacancies from GGA+U Calculations (2013)
    Hindawi
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    Publication Date: 2013-02-18
    Description: We have systematically studied the photocatalytic mechanisms of nitrogen doping in anatase TiO2 using first-principles calculations based on density functional theory, employing Hubbard U (8.47 eV) on-site correction. The impurity formation energy, charge density, and electronic structure properties of TiO2 supercells containing substitutional nitrogen, interstitial nitrogen, or oxygen vacancies were evaluated to clarify the mechanisms under visible light. According to the formation energy, a substitutional N atom is better formed than an interstitial N atom, and the formation of an oxygen vacancy in N-doped TiO2 is easier than that in pure TiO2. The calculated results have shown that a significant band gap narrowing may only occur in heavy nitrogen doping. With light nitrogen doping, the photocatalysis under visible light relies on N-isolated impurity states. Oxygen vacancies existence in N-doped TiO2 can improve the photocatalysis in visible light because of a band gap narrowing and n-type donor states. These findings provide a reasonable explanation of the mechanisms of visible light photocatalysis in N-doped TiO2.
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    Tailoring the Spectra of White Organic Light-Emitting Devices by Trap Effect of a Concentration-Insensitive Dopant (2013)
    Hindawi
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    Publication Date: 2013-02-20
    Description: Highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by using a novel iridium complex, bis[2-(,-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,]iridium(III) (acetylacetonate) [(tbpbt)2Ir(acac)], as the emitter. With a wide doping ratio ranging from 15 wt% to 25 wt%, the PhOLEDs maintained a comparable high performance, indicating concentration-insensitive property of the (tbpbt)2Ir(acac). On the basis of the unique characteristic of concentration insensitivity, the application of this phosphor was explored by fabricating white organic light-emitting devices (WOLEDs) with altered doping ratio, indicating that trap effect of (tbpbt)2Ir(acac) could effectively tailor WOLEDs spectra. Typically, a high-power efficiency, current efficiency, and external quantum efficiency of 30.0 lm/W, 38.8 cd/A, 18.1%, were achieved by 20 wt% doped WOLEDs.
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    Reliable and Damage-Free Estimation of Resistivity of ZnO Thin Films for Photovoltaic Applications Using Photoluminescence Technique (2013)
    Hindawi
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    Publication Date: 2013-02-20
    Description: This work projects photoluminescence (PL) as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO) thin films. ZnO thin films, deposited using chemical spray pyrolysis (CSP) by varying the deposition parameters like solvent, spray rate, pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the luminescence properties as well as resistivity. Two emissions could be recorded for all samples—the near band edge emission (NBE) at 380 nm and the deep level emission (DLE) at ~500 nm which are competing in nature. It is observed that the ratio of intensities of DLE to NBE (/) can be reduced by controlling oxygen incorporation in the sample. - measurements indicate that restricting oxygen incorporation reduces resistivity considerably. Variation of / and resistivity for samples prepared under different deposition conditions is similar in nature. / was always less than resistivity by an order for all samples. Thus from PL measurements alone, the order of resistivity of the samples can be estimated.
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    Synthesis, Characterization, and Photocatalytic Activity of N-Doped ZnO/ZnS Composites (2013)
    Hindawi
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    Publication Date: 2013-02-04
    Description: The aim of the present study is to enhance photocatalytic performance of ZnO semiconductor by comodification with doping of nonmetal ions and coupling with another semiconductor. Therefore, we synthesized the N-doped ZnO/ZnS photocatalysts via a simple heat-treatment approach using L-cysteine as N and S source in this work. Anthraquinone dye (reactive brilliant blue KNR) is employed as the model contaminants to evaluate the photocatalytic activity of as-synthesized samples under sunlight illumination. The N-doped ZnO/ZnS synthesized by this method shows better photocatalytic activity as compared to that of pure ZnO. The enhanced photocatalytic activity of the N-doped ZnO/ZnS composites may be related to the existence of N doping, ZnS/ZnO heterostructure, and covered abundant carbon species on the photocatalyst surface, which causing high absorption efficiency of light, efficient separation of electron-hole pairs, and quick surface reaction in doped ZnO.
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    Two- and Three-Component Visible Light Photoinitiating Systems for Radical Polymerization Based on Onium Salts: An Overview of Mechanistic and Laser Flash Photolysis Studies (2012)
    Hindawi
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    Publication Date: 2012-08-28
    Description: A review of our work on two- and-three component photoinitiator systems is presented. The emphasis is in on visible light polymerization in aqueous media. The systems discussed comprise a synthetic dye as sensitizer and an onium salt as coinitiator, or a dye-amine-onium salt with the amine as coinitiator and the onium salt as an enhancer of the polymerization efficiency. The effect of the composition of the system on the photopolymerization kinetics was analyzed. To this end, the photophysics and photochemistry of the dye under polymerization conditions was explored by means of stationary and time-resolved spectroscopic methods. Different dyes and onium salts were investigated. The action mechanism of the different photoinitiators systems is discussed.
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    Photocatalytic Activity of Nanostructured Titanium Dioxide Thin Films (2012)
    Hindawi
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    Publication Date: 2012-08-29
    Description: The aim of this paper is to investigate the properties and photocatalytic activity of nanostructured TiO2 layers. The glancing angle deposition method with DC sputtering at low temperature was applied for deposition of the layers with various columnar structures. The thin-film structure and surface morphology were analyzed by XRD, SEM, and AFM analyses. The photocatalytic activity of the films was determined by the rate constant of the decomposition of the Acid Orange 7. In dependence on the glancing angle deposition parameters, three types of columnar structures were obtained. The films feature anatase/rutile and/or amorphous structures depending on the film architecture and deposition method. All the films give the evidence of the photocatalytic activity, even those without proved anatase or rutile structure presence. The impact of columnar boundary in perspective of the photocatalytic activity of nanostructured TiO2 layers was discussed as the possible factor supporting the photocatalytic activity.
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    Silicon Nitride Film by Inline PECVD for Black Silicon Solar Cells (2012)
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    Publication Date: 2012-08-23
    Description: The passivation process is of significant importance to produce high-efficiency black silicon solar cell due to its unique microstructure. The black silicon has been produced by plasma immersion ion implantation (PIII) process. And the Silicon nitride films were deposited by inline plasma-enhanced chemical vapor deposition (PECVD) to be used as the passivation layer for black silicon solar cell. The microstructure and physical properties of silicon nitride films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry, and the microwave photoconductance decay (μ-PCD) method. With optimizing the PECVD parameters, the conversion efficiency of black silicon solar cell can reach as high as 16.25%.
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    PV Power-Generation System with a Phase-Shift PWM Technique for High Step-Up Voltage Applications (2012)
    Hindawi
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    Publication Date: 2012-07-20
    Description: A PV power-generation system with a phase-shift pulse-width modulation (PWM) technique for high step-up voltage applications is proposed. The proposed power-generation system consists of two stages. In the input stage, all power switches of the full-bridge converter with phase-shift technique can be operated with zero-current switching (ZCS) at turn-on or turn-off transition. Hence, the switching losses of the power switches can be reduced. Then, in the DC output stage, a voltage-doubler circuit is used to boost a high dc-link bus voltage. To supply a utility power, a dc/ac inverter is connected to induce a sinusoidal source. In order to draw a maximum power from PV arrays source, a microcontroller is incorporated with the perturbation and observation method to implement maximum power point tracking (MPPT) algorithm and power regulating scheme. In this study, a full load power of 300 W prototype has been built. Experimental results are presented to verify the performance and feasibility of the proposed PV power-generation system.
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    Preparation and Properties of SnO2 Film Deposited by Magnetron Sputtering (2012)
    Hindawi
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    Publication Date: 2012-07-26
    Description: Tin oxide SnO2 films were prepared by RF magnetron sputtering. The effects of oxygen partial pressure percentage on the SnO2 property have been investigated to obtain relatively high-resistivity SnO2 films which could be used as buffer layers to optimize the performance of CdTe/CdS solar cells. The oxygen partial pressure percentage varied in the range of 1%~10%. The results show that the introduction of oxygen would suppress the deposition and growth of SnO2 films. Electrical measurement suggests that the film resistivity decreases with the increase of oxygen pressure. The SnO2 films with resistivity of 232 Ω cm were obtained in pure Ar atmosphere. All SnO2 films fabricated with different oxygen partial pressure percentage have almost the same optical band gap.
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    Effect of Fe Concentration on Fe-Doped Anatase TiO2 from GGA + U Calculations (2012)
    Hindawi
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    Publication Date: 2012-07-16
    Description: To comprehend the photocatalytic mechanisms of anatase Ti1-xFexO2 with various concentrations of Fe, this study performed first principles calculations based on density functional theory with Hubbard U on-site correction to evaluate the crystal structure, impurity formation energy, and electronic structure. We adopted the effective Hubbard U values of 8.47 eV for Ti 3d and 6.4 eV for Fe 3d. The calculations show that higher concentrations of Fe are easily formed in anatase TiO2 due to a reduction in the formation energy. The band gap of Fe-doped TiO2 decreases Fe doping level increases as a result of the overlap among the Fe 3d, Ti 3d, and O 2p states, which enhances photocatalytic activity in the visible light region. Additionally, a broadening of the valence band and Fe impurity states within the band gap might also contribute to the photocatalytic activity.
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    Photomechanical Energy Conversion of Photoresponsive Fibers Exhibiting Bending Behavior (2012)
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    Publication Date: 2012-09-14
    Description: Photoresponsive fibers based on poly(acrylamide) (PAA) with methylene blue (MB) dye were prepared. All semicircular fibers show bending towards the direction of the flat surface of the fiber when illuminated. The fibers recover their initial shape when the illumination stops. The fiber is heated upon illumination and cooled to room temperature once the illumination is stopped. The fiber also is sensitive to humidity, showing bending behavior towards the direction of the flat surface of the fiber upon changing the humidity. The mechanical energy of the PAA/MB fiber is approximately 0.6 mN for the bending direction when it is illuminated. A possible mechanism for the bending behavior is as follow: (1) the fiber is heated upon illumination because of the photothermal effect, (2) the fiber loses water molecules, (3) the fiber shrinks; bending towards the direction of the flat surface of the fiber occurs because of a difference in the shrinkage for the flat surface and the other side of the fiber. Finally, we demonstrated that a PP ball (1.5 mg) can be moved by the mechanical energy produced by the changing shape of the fiber upon illumination.
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    Current Mechanism in HfO2-Gated Metal-Oxide-Semiconductor Devices (2012)
    Hindawi
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    Publication Date: 2012-06-20
    Description: The present study aimed to examine the current density-voltage (J-V) characteristics of Al/HfO2/p-Si (MOS) structure at temperatures ranging between 100 and 320 K and to determine the structure’s current transport mechanism. The HfO2 film was coated on a single side of the p-Si (111) crystal using the spin coating method. The J-V measurements of the obtained structure at the temperatures between 100 and 320 K revealed that the current transport mechanism in the structure was compatible with the Schottky emission theory. The Schottky emission theory was also used to calculate the structure’s Schottky barrier heights (ϕB), dielectric constants (εr) and refractive index values of the thin films at each temperature value. The dielectric constant and refractive index values were observed to decrease at decreasing temperatures. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of Al/HfO2/p-Si (MOS) structure was measured in the temperature range of 100–320 K. The values of measured C and G/ω decrease in accumulation and depletion regions with decreasing temperature due to localized Nss at Si/HfO2 interface.
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    Construction and Study of Hetreojunction Solar Cell Based on Dodecylbenzene Sulfonic Acid-Doped Polyaniline/n-Si (2012)
    Hindawi
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    Publication Date: 2012-07-10
    Description: Polyaniline/n-type Si heterojunctions solar cell are fabricated by spin coating of soluble dodecylbenzene sulfonic acid (DBSA)-doped polyaniline onto n-type Si substrate. The electrical characterization of the Al/n-type Si/polyaniline/Au (Ag) structure was investigated by using current-voltage (I-V), capacitance-voltage (C-V), and impedance spectroscopy under darkness and illumination. The photovoltaic cell parameters, that is, open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and energy conversion efficiency (η) were calculated. The highest Jsc, Voc, and efficiency of these heterojunctions obtained using PANI-DBSA as a window layer (wideband gap) and Au as front contact are 1.8 mA/cm2, 0.436 V, and 0.13%, respectively. From Mott-Schottky plots, it was found that order of charge carrier concentrations is 3.5×1014 and 1.0×1015/cm3 for the heterojunctions using Au as front contact under darknessness and illumination, respectively. Impedance study of this type of solar cell showed that the shunt resistance and series resistance decreased under illumination.
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    Influence of Alkaline Treatment with Ammonia Water on the Properties of PEDOT: PSS Films (2012)
    Hindawi
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    Publication Date: 2012-06-14
    Description: A study on the influence of alkaline treatment on the properties of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT: PSS) film is presented in this paper. The treatment is carried out using ammonia water (AW) solutions with various volumes. We have also examined the performance of organic solar cells (OSCs) with the undoped and AW-doped PEDOT:PSS layers. Results show that the acidity of PEDOT:PSS solution can be significantly reduced by adding the AW solution with the optimized volume ratio ≤9%, v/v, while the AW-doped PEDOT:PSS film shows an improved optical transmission and stabilized conductivity. However, compared to the pristine OSC without adding AW to the whole-extraction layer, the AW-doped OSC shows a slight degradation in the power conversion efficiency (from 2.12% to 2.02%), which has been attributed to the decreased Vo c and FF of devices after the addition of AW.
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    Photodegradation of Rhodamine B in Presence of CaO and NiO-CaO Catalysts (2012)
    Hindawi
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    Publication Date: 2012-06-25
    Description: A CaO catalyst was prepared by mild calcination (650°C) of facilely precipitated Ca(OH)2 and compared to an NiO-CaO catalyst obtained from an Ni(OH)2/Ca(OH)2 coprecipitate as a precursor. Both catalysts degraded rhodamine B (RB) effectively when exposed to ultraviolet light but exhibited slower degradation under visible light conditions. Under UV light, CaO was more effective than NiO-CaO, while in visible light, the opposite was observed. A mechanistic study revealed no influence of the specific surface area of the catalysts on RB degradation, no adsorption of RB on the positively charged surfaces of the catalysts, and only incomplete degradation of RB. Consequently, both materials represent nonconventional photocatalysts.
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    Assessment of Artificial Neural Networks for Hourly Solar Radiation Prediction (2012)
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    Publication Date: 2012-06-25
    Description: This paper presents an assessment for the artificial neural network (ANN) based approach for hourly solar radiation prediction. The Four ANNs topologies were used including a generalized (GRNN), a feed-forward backpropagation (FFNN), a cascade-forward backpropagation (CFNN), and an Elman backpropagation (ELMNN). The three statistical values used to evaluate the efficacy of the neural networks were mean absolute percentage error (MAPE), mean bias error (MBE) and root mean square error (RMSE). Prediction results show that the GRNN exceeds the other proposed methods. The average values of the MAPE, MBE and RMSE using GRNN were 4.9%, 0.29% and 5.75%, respectively. FFNN and CFNN efficacies were acceptable in general, but their predictive value was degraded in poor solar radiation conditions. The average values of the MAPE, MBE and RMSE using the FFNN were 23%, −.09% and 21.9%, respectively, while the average values of the MAPE, MBE and RMSE using CFNN were 22.5%, −19.15% and 21.9%, respectively. ELMNN fared the worst among the proposed methods in predicting hourly solar radiation with average MABE, MBE and RMSE values of 34.5%, −11.1% and 34.35%. The use of the GRNN to predict solar radiation in all climate conditions yielded results that were highly accurate and efficient.
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    Solar Energy Prediction for Malaysia Using Artificial Neural Networks (2012)
    Hindawi
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    Publication Date: 2012-06-04
    Description: This paper presents a solar energy prediction method using artificial neural networks (ANNs). An ANN predicts a clearness index that is used to calculate global and diffuse solar irradiations. The ANN model is based on the feed forward multilayer perception model with four inputs and one output. The inputs are latitude, longitude, day number, and sunshine ratio; the output is the clearness index. Data from 28 weather stations were used in this research, and 23 stations were used to train the network, while 5 stations were used to test the network. In addition, the measured solar irradiations from the sites were used to derive an equation to calculate the diffused solar irradiation, a function of the global solar irradiation and the clearness index. The proposed equation has reduced the mean absolute percentage error (MAPE) in estimating the diffused solar irradiation compared with the conventional equation. Based on the results, the average MAPE, mean bias error and root mean square error for the predicted global solar irradiation are 5.92%, 1.46%, and 7.96%. The MAPE in estimating the diffused solar irradiation is 9.8%. A comparison with previous work was done, and the proposed approach was found to be more efficient and accurate than previous methods.
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    Low-Level Laser Therapy and Calcitonin in Bone Repair: Densitometric Analysis (2012)
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    Publication Date: 2012-06-11
    Description: The aim of this work was to evaluate the association of low-level laser therapy (LLLT, 830 nm) and calcitonin in bone repair considering that bone healing remains a challenge to health professionals. Calcitonin has antiosteoclastic action and LLLT is a treatment that uses low-level lasers or light-emitting diodes to alter cellular function. Both are used to improve bone healing. Densitometry is a clinical noninvasive valuable tool used to evaluate bone mineral density (BMD). Sixty male rats were submitted to bone defect with a trephine bur, randomly divided into four groups of 15 animals each: control (C); synthetic salmon calcitonin (Ca); LLLT (La); LLLT combined with calcitonin (LaCa). Animals from Ca and LaCa received 2 UI/Kg synthetic salmon calcitonin intramuscularly on alternate days after surgery. Animals from groups La and LaCa were treated with infrared LLLT (830 nm, 10 mW, 20 J/cm2, 6 s, contact mode). Five animals from each group were euthanized 7, 14, and 21 days after surgery and bone defects were analyzed by densitometry. Statistical analysis showed a significant difference in BMD values in LaCa group at 7 and 21 days (P=0,005). The results of the densitometric study showed that LLLT (830 nm) combined with calcitonin improved bone repair.
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    Influence of the Sol-Gel pH Process and Compact Film on the Efficiency of TiO2-Based Dye-Sensitized Solar Cells (2012)
    Hindawi
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    Publication Date: 2012-04-23
    Description: The influence of pH during hydrolysis of titanium(IV) isopropoxide on the morphological and electronic properties of TiO2 nanoparticles prepared by the sol-gel method is investigated and correlated to the photoelectrochemical parameters of dye-sensitized solar cells (DSCs) based on TiO2 films. Nanoparticles prepared under acid pH exhibit smaller particle size and higher surface area, which result in higher dye loadings and better short-circuit current densities than DSCs based on alkaline TiO2-processed films. On the other hand, the product of charge collection and separation quantum yields in films with TiO2 obtained by alkaline hydrolysis is c.a. 27% higher than for the acid TiO2 films. The combination of acid and alkaline TiO2 nanoparticles as mesoporous layer in DSCs results in a synergic effect with overall efficiencies up to 6.3%, which is better than the results found for devices employing one of the nanoparticles separately. These distinct nanoparticles can be also combined by using the layer-by-layer technique (LbL) to prepare compact TiO2 films applied before the mesoporous layer. DSCs employing photoanodes with 30 TiO2 bilayers have shown efficiencies up to 12% higher than the nontreated photoanode ones. These results can be conveniently used to develop optimized synthetic procedures of TiO2 nanoparticles for several dye-sensitized solar cell applications.
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    Electrodeposited CuInS2 Using Dodecylbenzene Sulphonic Acid As a Suspending Agent for Thin Film Solar Cell (2012)
    Hindawi
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    Publication Date: 2012-04-23
    Description: CulnS2 thin films were electrochemically deposited onto fluoride-doped tin oxide (FTO) substrate in presence of dodecylbenzene sulphonic acid to adjust pH of the solution and as a suspending agent for the sulfur. Cyclic voltammetry and chronoamperometry were carried out to determine the optimum pH. The composition, crystallinity, and optical properties of the compounds synthesized were studied by energy dispersive X-ray (EDX), X-ray diffraction, and UV-Visible spectra. It was found that the increasing of pH shifts the electrodeposited voltage toward more negative and lowers the deposition current. It was concluded that CuInS2 with atomic stoichiometric ratio was prepared at pH equal to 1.5 and 150 ml of 0.1 M sodium thiosulphate, 5 ml of 0.1 M indium chloride, and 5 ml of 0.1 M cupper chloride. The energy gaps were calculated to be 1.95 and 2.2 eV for CuInS2 prepared at 1.5 and 2.5 of pH, respectively. It was found that Jsc, Voc, and η are 1.02×10−4 A/cm2, 0.52 V, and 1.3×10−2%, respectively, for FTO/CuInS2/ZnO/FTO heterojunction solar cell.
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    Photophysical Parameters, Excitation Energy Transfer, and Photoreactivity of 1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOP) Laser Dye (2012)
    Hindawi
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    Publication Date: 2012-06-05
    Description: The effect of solvents on the absorption and emission spectra of 1,4-bis(5-phenyl-2-oxazolyl)benzene (POPOP) laser dye has been studied in various solvents at 298 K. A bathochromic shift was observed in absorption and fluorescence spectra upon increase of solvent polarity, which indicates that this transition is π-π*. The ground and excited state dipole moments were calculated as 2.23 and 6.34 Debye, respectively. The dye solution in MeOH, n-heptane, and methyl isobutyl ketone gives laser emission in the blue region upon excitation by a 337.1 nm nitrogen pulse; the gain coefficient and emission cross section as well as normalized photostability have been determined. Excitation energy transfer from POPOP to rhodamine B and fluorescine was studied to improve the laser emission from these dyes. Such an energy transfer dye laser system (ETDL) obeys a long range columbic energy transfer mechanism with a critical transfer distance, R0, of 25 and 33 Å and kq equal to 10.4×1012 and 26.2×1012 M−1 s −1 for the POPOP/RB and POPOP/fluorescine pair, respectively. The POPOP dye is highly photostable in polar protic and polar aprotic solvents, while it displays photodecomposition in chloromethane solvent via formation of a contact ion pair. The photochemical quantum yield and rate of photodecomposition depend on the electron affinity of solvent.
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    Synthesis and Characterization of K-Ta Mixed Oxides for Hydrogen Generation in Photocatalysis (2012)
    Hindawi
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    Publication Date: 2012-06-11
    Description: K-Ta mixed oxides photocatalysts have been prepared by impregnation followed by calcination. The influence of the reaction temperature (450°C–900°C) on the phase formation, crystal morphology, and photocatalytic activity in hydrogen generation of the produced materials was investigated. The detailed analysis has revealed that all products exhibit high crystallinity and irregular structure. Moreover, two different crystal structures of potassium tantalates such as KTaO3 and K2Ta4O11 were obtained. It was also found that the sample composed of KTaO3 and traces of unreacted Ta2O5 (annealed at 600°C) exhibits the highest activity in the reaction of photocatalytic hydrogen generation. The crystallographic phases, optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-ray spectrometer (EDX) as its mode.
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    Quantification of Power Losses of the Interdigitated Metallization of Crystalline Silicon Thin-Film Solar Cells on Glass (2012)
    Hindawi
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    Publication Date: 2012-04-24
    Description: The metallization grid pattern is one of the most important design elements for high-efficiency solar cells. This paper presents a model based on the unit cell approach to accurately quantify the power losses of a specialized interdigitated metallization scheme for polycrystalline silicon thin-film solar cells on glass superstrates. The sum of the power losses can be minimized to produce an optimized grid-pattern design for a cell with specific parameters. The model is simulated with the standard parameters of a polycrystalline silicon solar cell, and areas for efficiency improvements are identified, namely, a reduction in emitter finger widths and a shift toward series-interconnected, high-voltage modules with very small cell sizes. Using the model to optimize future grid-pattern designs, higher cell and module efficiencies of such devices can be achieved.
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    Free Radical Shadow Cure Initiated Using Two-Component and Three-Component Initiator Systems (2012)
    Hindawi
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    Publication Date: 2012-05-08
    Description: In photopolymerization systems, “shadow cure” may be defined as polymerization which extends into regions which are not illuminated by the incident initiating light source. The objective of this study is to evaluate the use of fluorescent additives for polymerization in masked regions that are unilluminated by the incident initiating light. Two different fluorescent dyes are investigated: fluorescein (FL) and eosin Y spirit soluble (EYss). A systematic series of studies was performed to characterize the effects of fluorescence intensity, the incident light intensity, and the presence of a diphenyl iodonium salt on the observed degree of shadow cure. It was concluded that shadow cure may be enhanced if one or more fluorescent compounds emit fluorescent light at wavelengths absorbed by the dye in a two- or three-component photoinitiator system. The addition of DPI to the two-component systems containing MDEA and FL or EYss led to a significant enhancement in the observed shadow cure. This result was attributed to the fact that DPI will increase both the number of active centers and the mobility of the active centers as a result of the electron transfer reactions in which it participates.
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    Highly Efficient Organic UV Photodetectors Based on Polyfluorene and Naphthalenediimide Blends: Effect of Thermal Annealing (2012)
    Hindawi
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    Publication Date: 2012-05-08
    Description: A solution-processed organic ultraviolet photodetector (UV-PD) is introduced. The active layer of the UV-PD consists of poly(9,9-dioctyl fluorenyl-2,7–yleneethynylene) (PFE) and N,N′-bis-n-butyl-1,4,5,8- naphthalenediimide (BNDI) with a weight ratio of 3 : 1 in chloroform. The effect of thermal annealing on the device properties was investigated from room temperature to 80°C. The full device structure of ITO/PEDOT:PSS/PFE:BNDI (3 : 1)/Al gave responsivity of 410 mA/W at −4 V under 1 mW/cm2 UV light at 368 nm when 60°C of annealing temperature was used during its preparation. The devices that were annealed over the crystallization temperature of PFE showed a charge transfer resistance increase and a mobility decrease.
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    High Improvement in Conversion Efficiency of μc-SiGe Thin-Film Solar Cells with Field-Enhancement Layers (2012)
    Hindawi
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    Publication Date: 2012-05-15
    Description: The improved performance for hydrogenated microcrystalline silicon-germanium (μc-Si1−xGex:H, x~0.1) p-i-n single solar cells with hydrogenated microcrystalline silicon (μc-Si:H) field-enhancement layers (FELs) is demonstrated for the first time. The fill factor (FF) and conversion efficiency (η) increase by about 19% and 28% when the thickness of the μc-Si FEL is increased from 0 to 200 nm, it is attributed to the longer hole life-time and enhanced electric field in the μc-Si0.9Ge0.1:H layer. Therefore, we can successfully manufacture high-performance μc-SiGe:H solar cells with the thickness of absorbers smaller than 1 μm by conducting FELs. Moreover, the simulation tool is used to simulate the current-voltage (J-V) curve, thus we can investigate the carrier transport in the absorber of μc-Si0.9Ge0.1:H solar cells with different EFLs.
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    Effect of Deoxycholic Acid on the Performance of Liquid Electrolyte Dye-Sensitized Solar Cells Using a Perylene Monoimide Derivative (2012)
    Hindawi
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    Publication Date: 2012-05-24
    Description: The effect of coadsorption with deoxycholic acid (DCA) on the performance of dye-sensitized solar cell based on perylene monoimide derivative (PCA) as sensitizer and liquid electrolyte had been investigated. The current-voltage characteristics under illumination and incident photon to current efficiency (IPCE) spectra of the DSSCs showed that the coadsorption of DCA with the PCA dye results in a significant improvement in short circuit photocurrent and slight increase in the open circuit photovoltage, which lead to an overall power conversion efficiency. The enhancement of short circuit current was attributed to the increased electron injection efficiency from the excited state of PCA into the conduction band of TiO2 and charge collection efficiency. The current-voltage characteristics in dark indicates a positive shift in the conduction which also supports the enhancement in the photocurrent. The coadsorption with DCA suppressed charge recombination as indicated from the electrochemical impedance spectra and thus improved the open circuit photovoltage.
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    Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects (2012)
    Hindawi
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    Publication Date: 2012-03-02
    Description: This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS), electrodeposition (ED), magnetic sputtering (MS), and high vacuum thermal evaporation (HVE) have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS), ease of constituent control (ED), high material incorporation (MS), and low temperature process (MS, HVE, ED). These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.
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    Optical and Morphological Properties of ZnO- and TiO2-Derived Nanostructures Synthesized via a Microwave-Assisted Hydrothermal Method (2012)
    Hindawi
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    Publication Date: 2012-03-01
    Description: A microwave-assisted hydrothermal method was used to synthesize ZnO and TiO2 nanostructures. The experimental results show that the method resulted in crystalline monodispersed ZnO nanorods that have pointed tips with hexagonal crystal phase. TiO2 nanotubes were also formed with minimum bundles. The mechanism for the formation of the tubes was validated by HRTEM results. The optical properties of both ZnO and TiO2 nanostructures showed characteristics of strong quantum confinement regime. The photoluminescence spectrum of TiO2 nanotubes shows good improvement from previously reported data.
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    Design and Implementation of a Simulator for Photovoltaic Modules (2012)
    Hindawi
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    Publication Date: 2012-03-01
    Description: Proposed in this paper is the development of a photovoltaic module simulator, one capable of running an output characteristic simulation under normal operation according to various electrical parameters specified and exhibiting multiple advantages of being low cost, small sized, and easy to implement. In comparison with commercial simulation tools, Pspice and Solar Pro, the simulator developed demonstrates a comparable I-V as well as a P-V output characteristic curve. In addition, a series-parallel configuration of individual modules constitutes a photovoltaic module array, which turns into a photovoltaic power generation system with an integrated power conditioner.
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    MPPT Based on Sinusoidal Extremum-Seeking Control in PV Generation (2012)
    Hindawi
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    Publication Date: 2012-03-08
    Description: The paper analyses extremum-seeking control technique for maximum power point tracking circuits in PV systems. Specifically, the paper describes and analyses the sinusoidal extremum-seeking control considering stability issues by means a Lyapunov function. Based on this technique, a new architecture of MPPT for PV generation is proposed. In order to assess the proposed solution, the paper provides some experimental measurements in a 100 W prototype which corroborate the effectiveness of the approach.
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    Simple Methods to Approximate CPC Shape to Preserve Collection Efficiency (2012)
    Hindawi
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    Publication Date: 2012-03-09
    Description: The compound parabolic concentrator (CPC) is the most efficient reflective geometry to collect light to an exit port. Anyway, to allow its actual use in solar plants or photovoltaic concentration systems, a tradeoff between system efficiency and cost reduction, the two key issues for sunlight exploitation, must be found. In this work, we analyze various methods to model an approximated CPC aimed to be simpler and more cost-effective than the ideal one, as well as to preserve the system efficiency. The manufacturing easiness arises from the use of truncated conic surfaces only, which can be realized by cheap machining techniques. We compare different configurations on the basis of their collection efficiency, evaluated by means of nonsequential ray-tracing software. Moreover, due to the fact that some configurations are beam dependent and for a closer approximation of a real case, the input beam is simulated as nonsymmetric, with a nonconstant irradiance on the CPC internal surface.
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