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 (I${}_i$) has a low formation energy similar to that of the iodine vacancy (V${}_I$) 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-N${}_{pyridine}$ and coordination bonds, not only successfully eliminates the I${}_i$ and dissociative I${}_2$ but also passivates the abundant V${}_I$. Furthermore, the two symmetric neighboring -NH${}_2$ 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 Pb${}^{2+}$, 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 CsPbI${}_{3-x}$Br${}_x$ films show better environmental stability. (© 2023 Wiley‐VCH GmbH)