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.