Parametric optimization of CsPbI₂Br/CsPbBr₃ heterojunction device structures for enhanced performance

Recently, CsPbI₂Br-based all-inorganic perovskites have been recognized as a prospective candidate for photovoltaic applications owing to their remarkable thermal stability. Nevertheless, the device's performance is substantially weakened by the severe energy band misalignment at the interfaces, as well as the high interfacial and bulk defect densities. In this numerical investigation, the SCAPS-1D simulator is employed to evaluate the photovoltaic properties of the heterojunction FTO/ETL/CsPbI₂Br/CsPbBr₃/flat-bands solar cell structure. This study first compares the photovoltaic output metrics of multiple electron transport layer-based CsPbI₂Br/CsPbBr₃ perovskite solar cells. According to the results, the device with ZnOS as the electron transport layer has superior photovoltaic characteristics. Furthermore, the impact of varying the bulk defect density, the defect density at both interfaces, the carrier's density, and the thickness of the absorber layer are all examined. In addition, the evaluation encompasses an investigation of the effect of parasitic resistances, operating temperature, and rear contact metal work function on the photovoltaic results. The optimized defect density in the perovskite and at both interfaces has been determined to be in the range of 1013-1014 cm−3, and the optimal thickness for the CsPbI₂Br absorber layer is 800 nm. The acceptor concentration in the CsPbI₂Br and CsPbBr₃ layer has been determined to be 1016 cm−3 and 1019 cm−3, respectively. The proposed structure obtained the maximum efficiency of 21.26%, a short circuit current density of 16.46 mA/cm2 a fill-factor of 86.74%, and an open circuit voltage of 1.48 V after optimizing all physical parameters. The findings of this study offer a practical approach and valuable insights for the advancement of all-inorganic perovskite solar cells that are both stable and highly efficient.