Control of CsPbI₂Br Perovskite Colloidal Dispersion with 4-Methoxybenzenethiol for Slow Nucleation in CsPbI₂Br Perovskite and Enhanced Solar Cell Performance

Inorganic CsPbI 2 Br perovskite exhibits high thermal stability and superior optoelectronic properties and thus has been widely used in perovskite solar cells as a light absorber. Nevertheless, the unsatisfactory perovskite quality and severe charge recombination remarkably restrict the performance of the CsPbI 2 Br device. Herein, a strategy of controlling CsPbI 2 Br perovskite colloidal dispersion with 4-methoxybenzenethiol (MeOBT) is proposed for modulating the perovskite crystallization process and promoting CsPbI 2 Br perovskite quality. MeOBT is introduced into the CsPbI 2 Br precursor solution as a coordination additive. The strong interaction between MeOBT molecules and the haloplumbate framework triggers the disassembly of the precursor colloids in the precursor solution, reducing the perovskite nucleation sites and decreasing the perovskite growth rate. The slow perovskite nucleation and low crystal growth rate lead to formation of a large-grain and high-quality CsPbI 2 Br perovskite film. In addition, MeOBT molecules adsorb on the final perovskite film surface, protecting the perovskite film and passivating perovskite surface defect. With these benefits, the carbon-based CsPbI 2 Br perovskite solar cell that delivers a high power conversion efficiency of 14.08% and preserves ∼90% of the initial efficiency after 480 h storage in ambient conditions is fabricated.