In situ Induced 2D Perovskite Enhances Buried Interface Passivation for Ambient‐Processed Efficient Perovskite Solar Cells

ABSTRACT 2D perovskites are widely used for passivating the top surface of 3D perovskite solar cells (PSCs). However, constructing 2D perovskite at the buried interface faces a critical challenge, due to dissolving the predeposited 2D layers or organic ammonium ligands by the solvents of 3D perovskite precursors. Herein, a preburied strategy is developed to induce the in situ formation of 2D perovskite layer at the SnO 2 /perovskite buried interface. The formation is facilitated by the cooperated effect of cation exchange with 3D perovskite and the strong anchoring of the functional groups with SnO 2 layer. The resulting 2D perovskite effectively improves crystallization and passivates defects of 3D perovskite, associated with the transition of tensile strain to compressive strain. Moreover, the preburied spacer cations not only reduce the agglomeration of SnO 2 nanoparticles and suppress oxygen vacancies defects, but promote the interfacial carrier transport with favorable band alignment. Consequently, the conversion efficiency of ambient‐processed PSCs has been improved significantly from 23.33% to 25.67%, retaining over 90% of initial values after storing in air for 2500 h or under one‐sun continuous illumination for 1000 h. This work provides a feasible strategy of controllable formation of 2D perovskite layers for passivating buried interface of highly efficient PSCs.