Optimization of AgSb(S_xSe_1-x)₃/Sb₂S₃ Two-Terminal Tandem Photovoltaic Devices

Ag-incorporated Sb₂ (S_xSe_1-x)₃ thin-film solar cells are potential candidates for efficient and low-cost photovoltaic devices. We have investigated two-terminal tandem solar cells with AgSb(S_xSe_1-x)₃ and Sb₂S₃ by modeling and simulating multiple device configurations. A tandem structure consists of a bottom AgSb(S_xSe_1-x)₃ solar cell and a top Sb₂S₃ solar cell with different bandgaps to selectively absorb targeted photon energy. To optimize the performance, each absorber layer thickness is also adjusted based on optimized sulfur concentration (x=0.2) of AgSb(S_xSe_1-x)₃ solar cells. The bandgap of AgSb (S_0.2Se_0.8)₃ bottom cells and Sb₂S₃ top cells are 1.19 eV and 1.7 eV, respectively. Using the filtered spectrum and the current matching techniques, AgSb(S_0.2Se_0.8)₃/Sb₂S₃ tandem devices show open circuit voltage (Voc) of 1.63 V, current density (Jsc) of 17.04 mA/cm², and fill factor (FF) of 62.94 %. Collective, the power conversion efficiency is 17.48 %. The optimized absorber thickness of the top layer is 610 nm while the bottom layer is 400 nm. The result indicates that the AgSb(S_0.2Se_0.8)₃/Sb₂S₃ tandem device is a promising candidate to further improve the efficiency of emerging thin-film solar cells.