A Self-Assembled 3D/0D Quasi-Core–Shell Structure as Internal Encapsulation Layer for Stable and Efficient FAPbI₃ Perovskite Solar Cells and Modules

FAPbI₃ perovskites have garnered considerable interest owing to their outstanding thermal stability, along with near-theoretical bandgap and efficiency. However, their inherent phase instability presents a substantial challenge to the long-term stability of devices. Herein, this issue through a dual-strategy of self-assembly 3D/0D quasi-core–shell structure is tackled as an internal encapsulation layer, and in situ introduction of excess PbI₂ for surface and grain boundary defects passivating, therefore preventing moisture intrusion into FAPbI₃ perovskite films. By utilizing this method alone, not only enhances the stability of the FAPbI₃ film but also effectively passivates defects and minimizes non-radiative recombination, ultimately yielding a champion device efficiency of 23.23%. Furthermore, the devices own better moisture resistance, exhibiting a T₈₀ lifetime exceeding 3500 h at 40% relative humidity (RH). Meanwhile, a 19.51% PCE of mini-module (5 × 5 cm²) is demonstrated. This research offers valuable insights and directions for the advancement of stable and highly efficient FAPbI₃ perovskite solar cells. © 2023 Wiley-VCH GmbH.