Comparative Study of the Electrical Properties of CZTS-TiO2 and CZTS-ZnO Heterojunctions for PV Applications

Two heterojunctions based on Cu₂ZnSnS₄ were obtained as thin films, on FTO glass, by spray pyrolysis deposition. The choice of the n-type layer (TiO₂ or ZnO) has impacted the nucleation and growth of the CZTS layers deposited on top. Crystalline thin films were obtained with drastically different morphologies. Small spherical grains promoted a better match at the interface between TiO₂ and CZTS, while the hexagonal plates of ZnO promoted discontinuations. Both junctions proved photosensitive and gave good rectifying behavior but efficiencies lower than 0.01% suggest charge recombination at the interface or in the CZTS layer.