The presence of residual/excess lead iodide (PbI2) in lead halide perovskites has been pivotal for advancing the efficiency of perovskite solar cells (PSCs), yet its chemically active nature poses severe stability challenges. Achieving optimal device performance without compromising long-term stability remains a critical hurdle in perovskite photovoltaic technologies. This review systematically analyzes the mechanistic role residual/excess PbI2 in PSCs, elucidating its impact on both device efficiency and stability. A series of recent strategies for regulating residual/excess PbI2 have been further summarized, including regulating the distribution of the residual PbI2, controlling the crystallization kinetics of PbI2, and eliminating the excess PbI2. By providing a comprehensive roadmap for balancing efficiency and stability, this work aims to guide the rational design of high-performance and long-term stable PSCs.
Chang et al. (Tue,) studied this question.