High‐Performance 2D Dion‐Jacobson Tin Perovskite Solar Cells with Improved Charge Separation and Extraction

Abstract 2D Dion–Jacobson (DJ) tin halide perovskites have been recognized as promising photovoltaic materials due to their structural stability and designable multifunctional spacer cations. However, insulating organic spacer cations will bring a dielectric confinement effect and quantum well structure. Usually, these 2D perovskites exhibit poor charge transport performance, which hinders the preparation of high‐efficiency solar cells. Here, compared with p ‐phenylenediammonium, a multiple‐ring aromatic amine 1,5‐naphthalenediammonium (15‐NDA) spacer is introduced. Theoretical simulation and experimental characterization demonstrate that 15‐NDA with extended π‐conjugation length has greater steric hindrance and can inhibit the formation of small n‐phase. It can weaken the dielectric confinement effect and quantum well confinement, thus improving the exciton dissociation. Additionally, the strong π – π conjugation of 15‐NDA can enhance the intermolecular interaction and help to prepare more uniform and dense films. Furthermore, the oxidation of Sn 2+ and I − and the corresponding defect state density can be effectively reduced. As a result, the corresponding devices show improved carrier diffusion length and fast carrier extraction. Therefore, the 2D DJ (15‐NDA)FA 3 Sn 4 I 13 solar cells achieve a record performance of 7.33% and demonstrate improved humidity and nitrogen stability. This work provides a new approach to optimize the device performance by structural design of the organic spacers.