Surface Passivation of Lead Halide Perovskite Semiconductors for Improved Stability and Performance

Abstract

Metal halide perovskites have emerged as one of the most promising classes of semiconductors for next-generation optoelectronic technologies, including solar cells, light-emitting diodes, and photodetectors. In photovoltaic devices, perovskites have achieved power conversion efficiencies that rival those of established commercial technologies. However, despite their remarkable progress, the widespread development of perovskite photovoltaics remains hindered by intrinsic instability and the presence of electronic defects, particularly those located at the surface. These surface defects play a crucial role in limiting performance, accelerating degradation, and mediating ionic and electronic processes that challenge long-term operational stability, making surface passivation a central focus in perovskite research for stable, high-efficiency devices. To address these challenges, a variety of surface passivation strategies have been developed to mitigate defect states and suppress nonradiative recombination. While these approaches have demonstrated substantial improvements in both performance and stability, their implementation across diverse perovskite compositions and synthetic routes remains nontrivial. The optimal passivation strategy often depends on subtle variations in chemistry, processing, and environmental conditions. Realizing effective passivation demands finely tuned treatment conditions that maximize benefits of defect suppression while minimizing unintended chemical or structural side effects. In this context, defect passivation represents both a scientific challenge and a technological opportunity to accelerate the path toward stable, commercially viable perovskite solar cells. This dissertation investigates how surface passivation can be used to control ion motion and optimize interfacial properties in lead halide perovskite semiconductors. First, we demonstrate how surface passivation can kinetically suppress light-induced halide migration, thereby enhancing the photostability of perovskites. Second, we investigate the effects of aminosilane-based treatments, highlighting the significance of optimized treatment conditions, while also revealing surface reactivities of these molecules with formamidinium cations, linking interfacial chemistry to changes in optoelectronic behavior. Overall, these studies establish molecular surface passivation as a powerful route to tune ion migration, stability, and performance in lead halide perovskites. They provide insights that can help bridge interfacial chemistry with the practical requirements of durable perovskite optoelectronic technologies.