Publication Date:
2015-10-15
Description:
While presence of Na is essential for the performance of high-efficiency Cu(In,Ga)Se 2 thin film solar cells, the reasons why addition of Na by post-deposition treatment is superior to pre-deposition Na supply—particularly at low growth temperatures—are not yet fully understood. Here, we show by X-ray diffraction and electron microscopy that Na impedes annihilation of stacking faults during the Cu-poor/Cu-rich transition of low temperature 3-stage co-evaporation and prevents Cu homogeneity on a microscopic level. Lower charge carrier mobilities are found by optical pump terahertz probe spectroscopy for samples with remaining high stacking fault density, indicating a detrimental effect on electronic properties if Na is present during growth.
Print ISSN:
0003-6951
Electronic ISSN:
1077-3118
Topics:
Physics
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