Influence of In2S3 film properties on the behavior of CuInS2/In2S3/ZnO type solar cells

Solar cells of CuInS₂/In₂S₃/ZnO type are studied as a function of the In₂S₃ buffer deposition conditions. In₂S₃ is deposited from an aqueous solution containing thioacetamide (TA), as sulfur precursor and In³⁺. In parallel, variable amounts of In₂O₃ are deposited that have an important influence on the buffer layer behavior. Starting from deposition conditions determined in a preliminary study, a set of parameters is chosen to be most determining for the buffer layer behavior, namely the solution temperature, the concentration of thioacetamide TA], and the buffer thickness. The solar cell results are discussed in relation with these parameters. Higher efficiency is attained with buffer deposited at high temperature (70 °C) and TA] (0.3 M). These conditions are characterized by short induction time, high deposition rate and low In₂O₃ content in the buffer. On the other hand, the film deposited at lower temperature has higher In₂O₃ content, and gives solar cell efficiency sharply decreasing with buffer thickness. This buffer type may attain higher conversion efficiencies if deposited on full covering very thin film.