Electrolytically deposited Cadmium Selenide Films for Photovoltaic Applications

1School of Electrical and Computer Eng., National Technical University of Athens, Zografou Campus, 15780, Athens, Greece

Abstract

CdSe films were electrodeposited on pure nickel substrates. The nickel substrate was polished to a mirror finish by Al₂O₃ paste, etched in 10% HCl solution for 40 s and rinsed thoroughly by de-ionized water. The deposition bath contained solutions with excessive Cd²⁺ (0.2M) from CdSO₄ and small amounts of SeO₂ (1x10^-3 M). The pH of the bath was adjusted to a value of 2.2 at RT by adding 10% H₂SO₄. The bath was first thermostated at the required temperature, which varied from 55°C to 65°C. Plating was accomplished at deposition potential 1000 mV (vs. Hg/Hg2SO4). The films formed had a uniform thickness and it was found to be approximately 2.0 μm thick (for 20 min electrodeposition process. The produced CdSe films were characterized by X-Ray diffraction and SEM. The induced semiconductor doping effect by thermal annealing in pure dry nitrogen gas was also investigated. Gold contacts were placed on top of the CdSe films, either by evaporation, or mechanically. Depending on the deposition parameters the electrical characteristics of the Ni/CdSe/Au structures may exhibit rectification properties. The optical excitation of the structure was investigated for various CdSe thicknesses.