Controllable Two-dimensional Perovskite Crystallization via Water Additive for High-performance Solar Cells

Steering the crystallization of two-dimensional (2D) perovskite film is an important strategy to improve the power conversion efficiency (PCE) of 2D perovskite solar cells (PVSCs). In this paper, the deionized water (H₂O) additive is introduced into the perovskite precursor solution to prepare high-quality 2D perovskite films. The 2D perovskite film treated with 3% H₂O shows a good surface morphology, increased crystal size, enhanced crystallinity, preferred orientation, and low defect density. The fabricated 2D PVSC with 3% H₂O exhibits a higher PCE compared with that without H₂O (12.15% vs 2.29%). Furthermore, the shelf stability of unsealed devices with 3% H₂O under ambient environment is significantly improved. This work provides a simple method to prepare high-quality 2D perovskite films for efficient and stable 2D PVSCs.