Homogeneous electrochemical deposition of in on a Cu-covered Mo substrate for fabrication of efficient solar cells with a CuInS2 photoabsorber

Article abstract of DOI:10.1016/j.electacta.2012.06.103

Electrochemical deposition of indium (In) on a copper-covered molybdenum-coated glass substrate from several acidic InCl₃ solutions was studied for fabrication of CuInS₂-based solar cells. When In was deposited using a simple acidic InCl₃ solution at -0.80 V (vs. Ag/AgCl), island-shaped growth was observed, whereas a homogeneous In film was obtained from InCl₃ solution containing citric acid and sodium citrate at -0.98 V (vs. Ag/AgCl). Electrochemical and structural analyses revealed that the citric acid additive had a function for smoothing the surface of the In deposit. The mixing with sodium citrate induced appreciable inhibition of H₂ evolution during the In deposition, leading to high current efficiency of >90%. The CuInS₂ film derived from the homogeneous In had a uniform thickness with a smooth surface, while the CuInS₂ film obtained from the island-shaped In deposit showed a large variation in thickness with recessed areas. The CuInS₂ film derived from the homogeneous In was showed better photoelectrochemical response than that of the film fabricated from the island-shaped In. As expected from these differences, the solar cell with an Al:ZnO/CdS/CuInS₂/Mo structure derived from the homogeneous In film showed the best conversion efficiency of 7.8% with relatively high reproducibility.