Investigation of enhanced conductivity in dye-coated tin oxide thin films using Hall voltage measurements

The effects of dye coatings upon the transport properties of tin oxide thin films are studied. Conductivity enhancement factors ranging in magnitude from 2 to 20 were observed in fully characterized films painted with a crystal violet dye derivative. The conductivity enhancement is shown to be due to a combination of mobility and carrier density increase. Both of these effects are attributed to a reduction in surface scattering within a highly conductive surface layer rather than to more exotic models such as exciton coupling of conduction electrons. Preliminary studies using Langmuir-Blodgett films of the crystal violet dye did not, however, produce an increase in the tin oxide film conductivity.