Simulation Analysis of Sb2Se3 Narrow Bandgap Hole Transport Layer in MAPbI3 Perovskite Solar Cells

Inorganic hole transport layers, such as metal oxides and compounds, have recently been frequently applied in perovskite solar cells (PSCs) due to their ability to improve the stability of the devices. Among them, it is believed that narrow bandgap inorganic hole transport layers can also improve the light absorption of PSCs. In this study, antimony selenide (Sb₂Se₃) with a bandgap of 1.06 eV was employed as a hole transport layer to improve the performance of MAPbI₃ PSCs. Through optimization of the thickness of Sb₂Se₃ and MAPbI₃ , it can be observed that the absorption spectrum of Sb₂Se₃-MAPbI₃ solar cell expanded from 830 nm to 1170 nm, and the light absorption was improved, resulting in an improved short-circuit current density (J_sc) and fill factor (FF). Additionally, the n-type TiO₂ window layer was optimized, establishing that a donor concentration (N_D) of 10¹⁸ cm^-3 in TiO₂, with a 0.05-nm-thick layer can achieve the best conversion efficiency, while maintaining bulk defect densities below 10¹³ cm^-3 in both Sb₂Se₃ and MAPbI₃. Comparative analysis of interface defects revealed that high defect densities at the Sb₂Se₃/MAPbI₃ interface affect the depletion region width and J_sc, and increases dark current density. When the defects at both the Sb₂Se₃/MAPbI₃ and MAPbI₃/TiO₂ interface are dominated by MAPbI₃, and both of the defect densities are less than or equal to 10¹¹ cm^-3, the device can achieve a conversion efficiency of 21.90%.