Theoretical Analysis on Interfacial Dynamics Between Charge Transport Layer and Different Absorbers in Pb-free All Inorganic Perovskites Solar Cells

Although perovskite solar cells (PSCs) have captured notable interest as a potential candidate for third-generation solar cells, due to their favorable optoelectronic properties, cost-effectiveness, and high efficiency, some issues related to device stability and toxicity of the perovskite (PSK) layer hinders the commercial viability of PSCs. The inherent instability of organic PSK halides and the toxicity of Pb has compelled researchers to focus on developing Pb-free all-inorganic PSCs by replacing the organic species with inorganic (Cs⁺) cations as a safer alternative. In this study, the SCAPS-1D simulator was employed to investigate the cell performances of all-inorganic Pb-free Cs-based PSCs with three different PSK layers (CsGeI₃, CsSnI₃, and Cs₂TiI₆) individually, where inorganic ZnO and CuSCN were used as the electron transport layer (ETL) and the hole transport layer (HTL), respectively. The Cs₂TiI₆-based PSC was found to have the best performance. Then, the defect tolerance level of the PSK layer and the impact of band offset on cell performances were investigated. The optimum values of the conduction band offset (CBO) and the valence band offset (VBO) were found to be 0 eV and between − 0.1 eV and 0 eV, respectively. Moreover, the effect of interface defects at the ETL/PSK and PSK/HTL interfaces on cell performance was also analyzed as a function of CBO and VBO and, for both cases, the interface defect tolerance limit was recorded as 10¹⁶ cm⁻². This study observed a high rate of recombination for negative values of CBO and VBO at the interfaces. Thus, these findings will guide researchers in developing high-performance PSCs with suitable inorganic Pb-free perovskite and charge transport layers.