Highly layer-oriented PbI${}_2$ films enabling all-air processed perovskite solar cells

The two-step sequential deposition method exhibits favorable operability for processing perovskite films. Due to the growth of the perovskite films largely depends on the pre-deposited PbI${}_2$ films, the porous and rough PbI${}_2$ films are expected to facilitate the penetration of the organic amine salts. However, in air conditions, the porous and rough PbI${}_2$ films also facilitate the penetration of the water molecules, thus leading to diminished crystallinity. Despite substantial efforts aimed at inhibiting the decomposition of perovskite films, the performance of air-processed perovskite solar cells (PSCs) remains unsatisfactory. Herein, the study presents that the PbI${}_2$ films with high exposure of layered planes and vanished of non-layered planes have more effective to resist water erosion and promote the crystallization process of perovskite films. An amphoteric Lewis acid-base molecule (cephalothin, a type of antibiotic) is added in PbI${}_2$ precursor solution to induce this highly layer-oriented PbI${}_2$ film. Consequently, the perovskite films can be processed under humidity condition and yield the champion PSC with an outstanding power conversion efficiency of 24.45%. In addition, the unencapsulated devices maintain 80% of their initial power conversion efficiency after 1000 h storage in air and exhibit high thermal stability after 100 cycles at 25-70 °C. (© 2024 Wiley‐VCH GmbH)