Competitive Formation Mechanism for Bidentate Passivation of Halogen Vacancies in Perovskite Based on 6‐Chloropurine

For metal halide perovskite solar cells, bidentate passivation (BP) is highly effective, but currently, only passivation sites rather than molecular environments are being considered. Here, the authors report an effective approach for high‐performance fully printable mesoscopic perovskite solar cells (FP‐PSCs) through the BP strategy using the multidentate molecule 6‐chloropurine (6‐CP). By utilizing density functional theory (DFT) calculations, X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) characterizations, the competition mechanism is identified of BP between the chlorine atom and neighboring nitrogen atom of the imidazole and pyrimidine rings. Through BP between the chlorine atom and adjacent nitrogen atom in imidazole, the power conversion efficiency (PCE) of the pristine samples is significantly enhanced from 16.25% to 17.63% with 6‐CP. The formation of BP enhances interfacial hole selectivity and charge transfer, and suppresses nonradiative recombination, improving device stability under high humidity conditions. The competition mechanism of BP between two aromatic cycles provides a path for designing molecular passivants and selecting passivation pathways to approach theoretical limits. For printable mesoscopic perovskite solar cells, bidentate passivation (BP) is an important approach to enhance their photovoltaic performance. Here, the competition mechanism is discovered between the chlorine atom of the multidentate molecule 6‐CP and the adjacent nitrogen atoms in the imidazole and pyrimidine rings. By utilizing the bidentate coordination between the chlorine atom and the nitrogen atom in the imidazole unit, the power conversion efficiency (PCE) is increased of the pristine sample from 16.25% to 17.63%. The formation of BP enhances the interface hole selectivity and charge transfer, suppresses nonradiative recombination, and improves the device stability under high humidity conditions.