Competitive Coordination Induced Crystallization Regulation for Efficient and Stable Sn‐Pb Perovskite Solar Cells

The faster crystallization rate of Sn perovskite compared with Pb perovskite leads to the spatial component inhomogeneity and inferior quality of the Sn‐Pb perovskite films, which increases the quasi‐Fermi level splitting (QFLS) deficit and accelerates the oxidative degradation of the films, thus undercutting the efficiency and stability of Sn‐Pb perovskite solar cells. Herein, we propose a thermodynamic selective strategy to mediate the crystallization rate between the Sn‐ and Pb‐based perovskite by introducing methyl 5‐aminolevulinate hydrochloride (5‐AH) in perovskite precursor solution. The SnI2 competes with PbI2 in coordinating with 5‐AH to form the thermodynamically favored SnI2‐5‐AH adducts with stronger SnI2‐Cl− according to molecular orbital interactions, thereby delaying the crystallization of Sn‐based perovskite. Such crystallization regulation improves the composition uniformity and the crystallization quality, which effectively suppresses non‐radiative recombination and reduces the QFLS deficit. Additionally, the strong interaction between Sn2+ and 5‐AH as well as reductive grain boundaries inhibits the oxidation of Sn2+. Therefore, the optimal devices with 5‐AH exhibit an improved PCE of 23.76% with a high voltage of 0.885 V and long‐term stability, maintaining 89% of initial efficiency under continuous irradiation for 1100 h at the maximum power point under AM 1.5G.