Methylammonium lead halide nanocubes templated by block copolymer colloids

Herein, we demonstrate effects of salt and methanol contents on the formation of methylammonium lead bromide (MAPbBr₃) nanocubes within supernatants, coexisting with MA₄PbBr₆ crystals in precipitates when a high methylammonium bromide (MABr) content is used. Our study demonstrates the role of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) block copolymer micellization in 1,3,5-trimethylbenzene (TMB), facilitating lead bromide complexation through hierarchical emulsion. In the presence of PS-b-PEO, PbBr₂ dissociates into [PbBr₃]⁻ and [PbBr₄]²⁻ complexes, which bind to the PEO block to form irregular nanosheets in TMB. The addition of MABr drives the crystallization of MAPbBr₃ nanocubes at the expense of these complexes. Methanol plays a critical role in solvating MA⁺ and Br⁻ ions, enhancing ion mobility and their interaction with the complexes. Without methanol, large MAPbBr₃ microparticles form from PbBr₂ microparticles, reducing nanocube formation. Optimizing the methanol and MABr content is crucial for minimizing defects, improving photoluminescence quantum yield (PLQY), prolonging photoluminescence lifetime, and preventing the formation of MA₄PbBr₆ microparticles, which persist in the precipitates. This work provides new insights into the role of solvent quality, methanol, and MABr concentration in the micellization of PS-b-PEO, PbBr₂ complexation, and the stabilization of MAPbBr₃ nanocubes.