Reactive passivation of wide-bandgap organic-inorganic perovskites with benzylamine

While amines are widely used as additives in metal-halide perovskites, our understanding of how amines in perovskite precursor solutions impact the resultant perovskite film is still limited. This study explores the multiple effects of benzylamine (BnAm), used to passivate both FA₀.₇₅Cs₀.₂₅Pb(I₀.₈Br₀.₂)₃ and FA₀.₈Cs₀.₂PbI₃ perovskite compositions. Unlike benzylammonium (BnA⁺) halide salts, BnAm reacts rapidly with formamidinium (FA⁺) cation, forming new chemical products that passivate perovskite crystal domains. The use of BnAm as a bulk additive increases the solar cell maximum power point tracked efficiency to 19.3%, with improved T80 stability under stress tests. This highlights mechanistic differences between amine and ammonium salt passivation, leading to improved material quality and device performance in perovskite solar cells.