Optimization of germanium-based perovskite solar cells by SCAPS simulation

In recent years, non-toxic germanium-based perovskite solar cells have attracted wide attention, but the efficiency is not high. We designed a new type of germanium-based perovskite structure to improve the efficiency (FTO/Cd0.5Zn0.5S/IDL1/CH3NH3GeI3/IDL2/MASnBr3/Au). We chose Cd0.5Zn0.5S and MASnBr3 as electron transport material (ETM) and hole transport material (HTM) respectively. Considering the interface recombination and interface quality, we added the interface defect layer (IDL1, IDL2) on both sides of the perovskite layer. We preliminarily simulated the designed battery structure with SCAPS and the results showed that the power conversion efficiency (PCE) was 13.18%. We analyzed the effects of key parameters of each layer, such as temperature, bandgap, thickness, electron affinity, defect density, on device performance and calculated the optimal value. Ge-based perovskite with high ionic conductivity and good electronic properties. Cd0.5Zn0.5S has higher electron quasi-Fermi level and MASnBr3 has lower hole quasi-Fermi level, which can better match the energy band of perovskite layer and promote the migration of carriers. Our optimized key parameters reduce the electron-hole recombination and enhance the photoelectric conversion efficiency of the battery. The PCE of the battery is 38.15% higher than before. Our simulation results provide a reference for the following study of Ge-based perovskites.