Improving Out‐of‐Plane Charge Mobility and Phase Stability of Dion‐Jacobson Lead‐Free Perovskites via Intercalating π‐Conjugated Aromatic Spacers

Abstract The layered quasi‐2D perovskites are recognized as one of the effective strategies to resolve the big problem of intrinsic phase instability of the perovskites. However, in such configurations, their performance is fundamentally limited due to the correspondingly weakened out‐of‐plane charge mobility. Herein, the π‐conjugated p‐phenylenediamine (PPDA) is introduced as organic ligand ions for rationally designing lead‐free and tin‐based 2D perovskites with the aid of theoretical computation. It is evidenced that both out‐of‐plane charge transport capacity and stability can be significantly enhanced within as‐established quasi‐2D Dion‐Jacobson (DJ) (PPDA)Cs_n‐1Sn_nI_3n+1 perovskites. The obviously increased electrical conductivity and reduced carrier effective masses are attributed to the enhanced interlayer interactions, limited structural distortions of diamine cations, as well as improved orbital coupling between Sn²⁺ and I⁻ ions of (PPDA)Cs_n‐1Sn_nI_3n+1 perovskites. Accordingly, by dimension engineering of the inorganic layer (n), the bandgap (E_g) of quasi‐2D perovskites can be linearly tailored toward the suitable E_g (1.387 eV) with optimal photoelectric conversion efficiency (PCE) of 18.52%, representing their great potential toward promising applications in advanced solar cells.