Integrative Enhancement of Energy‐Level Alignment and Defect Passivation for High‐Performance Lead‐Free Perovskite Solar Cells

Abstract CsGeI 2 Br‐based perovskites with a favorable bandgap and high absorption coefficient, show great promise as candidates for efficient lead‐free perovskite solar cells (PSCs). However, the significant defect recombination and energy alignment mismatch at the perovskite‐transport layer interface limit both the device's performance and long‐term stability. To overcome these challenges, the photovoltaic potential of the device is unlocked by optimizing the optical and electronic parameters through a rigorous numerical simulation, including the transport layer materials, doping density, bulk/interface defect density, and carrier mobility. As a result, the optimized device achieved a champion power conversion efficiency of 28.00%. To further elucidate the inherent physical behavior, the activator energy of carrier recombination, along with the conduction and valence band offsets, are also investigated. Additionally, different types of device structures, including p‐i‐n and HTL‐free structures, are briefly examined. Finally, a detailed roadmap for enhancing the efficiency of the device is proposed, offering valuable insights for improving inorganic lead‐free CsGeI 2 Br perovskite solar cells in optoelectronic applications.