Defect States And Charge Carrier Dynamics In Lead-Free Metal Halide Perovskites

Abstract

Metal halide perovskites (MHPs) have gained considerable attention as efficient light-absorbing and charge- transporting materials for next-generation photovoltaic systems. Extensive experimental and theoretical studies, particularly on lead-based systems, have significantly advanced the understanding of defect states and their impact on charge carrier dynamics. However, despite these advances and continued progress in defect engineering, the fundamental nature of intrinsic and extrinsic defects, especially in emerging lead-free perov skites, remains incompletely understood due to strong electron-phonon coupling and ionic lattice softness. This review systematically analyzes defect physics in MHPs, focusing on defect formation and its roles in charge trapping and recombination. It further discusses state-of-the-art characterization techniques and theoretical approaches, particularly density functional theory (DFT), used to model defect states in crystalline and poly crystalline films. Strategies for defect passivation and performance enhancement are also evaluated to improve device efficiency and long-term stability. Importantly, this review synthesizes underrepresented computational studies on lead-free perovskites and enhances earlier reviews that predominantly emphasize either experimental defect characterization or lead-based materials. By correlating computational predictions with experimental observations, this review aims to advance a more complete understanding of defect-mediated processes in MHPs and suggest the rational design of environmentally benign, high-performance perovskite optoelectronic materials.