Low-Temperature Stable α-Phase Inorganic Perovskite Compounds via Crystal Cross-Linking

Inorganic perovskite compounds hold promise to improve the stability of perovskite solar cells (PSCs). However, the phase instability and high annealing temperature process of these metastable structural polymorphs such as α-phase CsPbI_{3- x}Br _x hinder their further development. Herein, we demonstrated the successful reduction of temperature from 250 to 100 °C during the growth of stable and high-crystallinity α-phase CsPbI₂Br via crystal cross-linking. 4-Aminobenzoic acid (ABA) was used as a nonvolatile additive with slight solubility in water to bridge the adjacent CsPbI₂Br to form a grain-interconnected film. The interaction between ABA and perovskite grains leads to the growth of highly crystalline perovskite films. The optimized PSC based on ABA-incorporated CsPbI₂Br using a TiO₂/Al₂O₃/NiO/carbon architecture exhibits an efficiency of 8.44%. More importantly, the additive enables significant improvement of phase stability against moisture. The good performance highlights the chemical modification via cross-linking to achieve efficient and stable inorganic perovskite devices.