This work investigates the growth mechanisms and optimization of optical properties in block copolymer (BCP)‐templated MAPbBr3 perovskite nanocrystals (PeNCs). Neutron scattering, transmission electron microscopy, and in situ optical spectroscopy studies combined with confinement‐model‐based size estimation of the nanocrystals during the perovskite formation revealed a complex multispecies growth behavior of BCP‐templated PeNCs, which was significantly influenced and could be controlled by systematically varying the stoichiometry between polystyrene‐b‐poly(2‐vinylpyridine) (PS‐b‐P2VP) and PbBr2 in the precursor, and the manner of adding the A‐cation either as a dispersion in a polymer solution or dissolved in methanol. The combination of optimized precursor stoichiometry and methanol‐based A‐cation addition yielded narrow emission linewidths of 83 meV and photoluminescence quantum yields of up to 87%. These findings provide new mechanistic insights and practical levers for improving BCP‐templated perovskite nanocrystals, paving the way for their application in future optoelectronic devices.
Ganswindt et al. (Sun,) studied this question.