Exploring Lysine Incorporation as a Strategy to Mitigate Postsynthetic Halide Exchange in Lead-Halide Hybrid Perovskites

Lead-halide hybrid perovskites (RNH₃PbX₃, X = halide, e.g., Cl, Br, I; R = organic moiety) show promise for next-generation optoelectronic devices due to their simple synthesis routes, strong light absorption, and high photoluminescence quantum yield. However, postsynthetic halide exchange in lead-halide perovskites poses a challenge for the functionality of many perovskite devices. For example, in all-perovskite heterostructures, halide diffusion results in the formation of undesired mixed alloys rather than sharp interfaces required for many optoelectronic applications. To address this issue, we incorporated lysine molecules, one of the 20 common amino acids, into a hybrid perovskite MAPbBr₃ (MA = CH₃NH₃) host and investigated their impact on the host’s ability to undergo postsynthetic halide exchange. We immersed lysine-incorporated MAPbBr₃ crystals in solutions containing Cl^- or I^- for varying durations and analyzed subsequent halide exchange-related changes using ion chromatography, high-resolution powder X-ray diffraction, and photoluminescence spectroscopy. Our findings unanimously indicate that incorporated lysine significantly impedes postsynthetic Cl⁻ and I⁻ diffusion into bulk MAPbBr₃. Our new bioinspired approach opens a route toward mitigating postsynthetic halide exchange in lead-halide hybrid perovskites and improving the suitability of perovskite devices for optoelectronic applications.