(AgxCu1 – x)2ZnSnS4-Based Thin Film Heterojunctions: Influence of CdS Deposition Method

Cu₂ZnSnSe₄ (CZTSe) based solar cells, containing abundant elements, with Ag alloying have recently reached efficiency of 10.2%. The open circuit voltage in CZTSe devices is believed to be limited, in between other factors, by strong band tailing caused by an exceptionally high density of Cu/Zn antisites. By replacing Cu in CZTSe with Ag, whose covalent radius is 15% larger than that of Cu and Zn, the density of I–II antisite defects (e.g., Cu–Zn disorder) is predicted to drop. In the present work, (Ag_xCu_1 – x)₂ZnSnS₄ (ACZTS) heterostructures in three different architectures were investigated. The 5 and 10% silver substituted CZTS absorber layers were obtained by low-cost spray pyrolysis technique, as well as three different methods for the CdS layer deposition were tested in order to optimize the ACZTS heterostructure efficiency.