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.