Construction of hole-free 2D c-WSe₂/3D CsSnI₃ perovskite heterojunction cells optimized using SCAPS-1D

Abstract Perovskite solar cells (PSCs) have made remarkable progress in power conversion efficiency, reaching 26%, but interfacial defects and operational instability continue to hinder their practical application. Two-dimensional (2D) c-WSe 2 has emerged as a promising solution to these challenges due to its bondless surface and ability to form van der Waals heterojunctions, which can improve interface quality and enhance device stability. Here, we investigate the effect of 2D c-WSe 2 on tin-based PSCs by constructing 2D c-WSe 2 /3D CsSnI 3 heterojunctions. A hole-free transport layer structure was used to reduce fabrication complexity and cost. We simulated and optimized cell performance using SCAPS-1D, comparing the effects of various electron transport layers (ETLs) and back electrodes. Our results show that selecting materials with energy level alignment to the absorption layer significantly enhances carrier transport efficiency and increases power conversion efficiency (PCE). Optimization of parameters such as the absorption layer thickness, c-WSe 2 band gap, interface defect layer (IDL1 and IDL2) thickness, and operating temperature further improved performance. Specifically, adjusting the band gap and layer thickness improved light absorption and aligned the band structure, promoting efficient carrier transport across the interface. The final optimized device achieved an open-circuit voltage (V oc ) of 1.23 V, short-circuit current density (J sc ) of 34.46 mA cm −2 , fill factor (FF) of 75.51%, and PCE of 32.12%. These results highlight the potential of 2D materials like c-WSe 2 in advancing heterojunction PSCs and improving the efficiency and stability, suggesting promising prospects for their practical application.