Efficient Liquid–Solid Coregulation Engineering in Mixed‐Cation Lead Mixed‐Halide Perovskite for Photovoltaic Performance Improvement

Mixed-cation lead mixed-halide perovskite have attracted extensive attention due to their application potential in tandem devices and favorable stability. However, the crystallization of mixed-component perovskite usually suffers from more complicated phase-transition processes, making it difficult to prepare high-quality perovskite films. Herein, it is demonstrated that rhodamine 110 chloride (RC110) additive, a commonly used fluorescent dye, plays significant roles in improving the performance of perovskite solar cells (PSCs). It is shown that the defects can be remarkably reduced by interactions between the defects and the functional groups, the interaction between the RC110 and halogen ions in precursor solution can exert significant effects on the coordination level of lead–halogen octahedral frameworks, and thereby augments the colloidal size in the precursor solution. Leveraging these benefits, the liquid–solid coregulation engineering endows high-quality perovskite films with enhanced crystallinity, lower defects density, reduced nonradiative recombination, and prolonged carrier lifetime. Consequently, the RC110-treated planar devices deliver a champion efficiency of 21.02% with negligible hysteresis and exhibit excellent stability. Briefly, this defect passivation strategy based on colloidal coordination engineering provides a novel and feasible route to promote the potential commercialization of PSCs.