Targeted Anchoring of All Cations with 5-Bromopyridine-3-sulfonic Acid for High-Performance Perovskite Solar Cells

The quality of organic–inorganic hybrid perovskite films directly affects the application prospect of perovskite solar cells (PSCs), where organic and inorganic cations are the core elements that affect the quality of the perovskite. The additive strategy has been widely used to passivate cation-related defects in perovskite films. Here, the perovskite precursor solution introduced 5-bromopyridine-3-sulfonic acid (BOH) with a potential all-cation passivation function. The experimental results verified that the N atom on pyridine in the BOH molecular structure passivated the defects in perovskite by binding with undercoordination Pb²⁺, and the sulfonic acid group inhibited nonradiative recombination through their interactions with FA⁺ and Pb²⁺, improving perovskite grain size and crystallinity, and enhancing film quality. Thanks to the all-cationic targeted anchoring effect of BOH, the efficiency of the BOH-treated device upgraded from 22.32 to 24.33%. Importantly, PSCs with BOH showed excellent stability after exposure to 25% humidity for 1200 h at room temperature.