High-Efficiency (>14%) and Air-Stable Carbon-Based, All-Inorganic CsPbI2Br Perovskite Solar Cells through a Top-Seeded Growth Strategy

The inferior crystallinity and phase stability of CsPbI2Br films have severely hindered the development of carbon-based, all-inorganic perovskite solar cells (PSCs). Herein, we demonstrate the preparation of CsPbI2Br films by the top-seeded solution growth (TSSG) technique. It is performed through spin-coating of CH3NH3Br (MABr) atop CsPbI2Br precursor film prior to annealing, during which perovskite seeds are generated atop it. These perovskite seeds not only serve as nuclei to regulate the growth of CsPbI2Br grains but also provide additional Br– anions to generate a thin Br-rich layer atop the final CsPbI2Br film. The former contributes to the formation of CsPbI2Br film with full coverage, larger grains, higher crystallinity, and fewer electronic defects, while the latter gives rise to residual compressive strain along the film and thus markedly boosts its phase stability. Consequently, the optimized carbon-based, all-inorganic PSC exhibits a much better efficiency of 14.84% coupled with favored storage and operational stability.