Defect Passivation Strategies in Halide Perovskite Solar Cells and LEDs.

Metal halide perovskites (MHPs) have rapidly emerged as a major focal point of modern materials research owing to their solution processability and attractive optoelectronic properties, including bright, efficient, and narrow luminescence. The rapid development of MHPs has largely been driven by their exceptional performance in solar cells, light-emitting diodes, and other optoelectronic devices. Although low-bandgap MHPs are defect-tolerant, their performance and stability in devices remain highly sensitive to surface and interfacial defects as well as grain boundaries. These imperfections hinder device performance by affecting charge-carrier transport within perovskite layers and across interfaces by introducing nonradiative recombination pathways. Consequently, the passivation of MHPs has emerged as a key driver in perovskite optoelectronics, advancing device efficiencies and long-term operational stability. This Review presents a state-of-the-art overview of defect types in bulk and nanocrystalline MHPs, and their effects on charge-carrier recombination. We also discuss passivation strategies and mechanisms, along with the passivator molecules that have been effective in enhancing the performance and stability of solar cells and LEDs. Ultimately, we highlight the outstanding challenges and future prospects.