Highly efficient and stable 2D–3D perovskite solar cells fabricated by interfacial modification

Two-dimensional (2D) perovskites, which have excellent stability compared with three-dimensional (3D) perovskites owing to the effective protection of the hydrophobic organic ligands, have become a research hotspot and have made great developmental progress in recent years. Herein, an n-butylammonium iodide (BAI) post-treatment process was developed to fabricate a 2D-3D hybrid perovskite with a thin layer of 2D perovskite covered on the surface of the 3D CH3NH3PbI3 perovskite. The growth process of 2D perovskite is formed through the chemical reaction between BAI and the residual PbI2, which improves stability and reduces the number of crystal defects of 3D perovskite by optimizing stoichiometry. Compared with the 3D counterpart, the 2D-3D hybrid perovskite shows outstanding light and air stability when exposed to external environments. Moreover, structure conversion from 3D to 2D-3D can induce the passivation of defects in the 3D films. The power conversion efficiency of the 2D-3D solar cell exceeds 18% and retains 80% of the initial value after more than 2000 h of storage without encapsulation.