Materials and Methods for Interface Engineering toward Stable and Efficient Perovskite Solar Cells

Because interfacial nonradiative recombination (NRR) has a significant influence on device performance, the minimization of interfacial NRR losses through interface engineering especially for perovskite-related interfaces is key to achieving efficient, stable, and hysteresis-free perovskite solar cells (PSCs). In light of important contributions of interface engineering to rapid development of PSCs, a systematic investigation and analysis on the latest research advancements on interface engineering is urgently needed. This Review aims at providing innovative insights into further improvement in power conversion efficiency (PCE) toward the Shockley-Queisser limit efficiency and stability fulfilling commercially available standard protocols as well as reduction of hysteresis. In this Review, the roles and importance of interfaces in PSCs are first highlighted from the viewpoint of device structure, working principles, and interfacial carrier dynamics. The main origins (i.e., interface defects, imperfect energy level alignment (ELA), and interfacial reactions) of interfacial NRR are then discussed in detail along with characterization techniques. Subsequently, the effects of interfacial NRR on PCE, stability, and hysteresis are investigated. Strategies for mitigating interfacial NRR are provided in terms of defect passivation, ELA modulation, and suppression of interfacial reaction, where the critical roles of functional groups of interface modifiers are emphasized. Finally, we provide an outlook for efficient, hysteresis-free, and long-term operationally stable PSCs achievable via interface engineering.