Managing Multiple Halide‐Related Defects for Efficient and Stable Inorganic Perovskite Solar Cells

Halide‐related surface defects on inorganic halide perovskite not only induce charge recombination but also severely limit the long‐term stability of perovskite solar cells. Herein, adopting density functional theory calculation, we verify that iodine interstitials (Ii) has a low formation energy similar to that of the iodine vacancy (VI) and is also readily formed on the surface of all‐inorganic perovskite, and it is regarded to function as an electron trap. We screen a specific 2,6‐diaminopyridine (2,6‐DAPy) passivator, which, with the aid of the combined effects from halogen‐Npyridine and coordination bonds, not only successfully eliminates the Ii and dissociative I2 but also passivates the abundant VI. Furthermore, the two symmetric neighboring ‐NH2 groups interact with adjacent halides of the octahedral cluster by forming hydrogen bonds, which further promotes the adsorption of 2,6‐DAPy molecules onto the perovskite surface. Such synergetic effects can significantly passivate harmful iodine‐related defects and undercoordinated Pb2+, prolong carrier lifetimes and facilitate the interfacial hole transfer. Consequently, these merits enhance the power‐conversion efficiency (PCE) from 19.6 % to 21.8 %, the highest value for this type of solar cells, just as importantly, the 2,6‐DAPy‐treated CsPbI3−xBrx films show better environmental stability. Multiple iodine‐related defects in CsPbI3−xBrx perovskite solar cells (PSCs) were inhibited by the synergistic effects of halogen, coordination, and hydrogen bonds of 2,6‐diaminopyridine (2,6‐DAPy). This results in an excellent power‐conversion efficiency of 21.8 % for the 2,6‐DAPy‐CsPbI3−xBrx PSCs, alongside significantly enhanced humidity stabilities of unencapsulated cells.