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

FAPbI 3 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 PbI 2 for surface and grain boundary defects passivating, therefore preventing moisture intrusion into FAPbI 3 perovskite films. By utilizing this method alone, not only enhances the stability of the FAPbI 3 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 T 80 lifetime exceeding 3500 h at 40% relative humidity (RH). Meanwhile, a 19.51% PCE of mini-module (5 × 5 cm 2 ) is demonstrated. This research offers valuable insights and directions for the advancement of stable and highly efficient FAPbI 3 perovskite solar cells.