Optical Properties of Colloidal CH₃NH₃PbBr₃ Nanocrystals by Controlled Growth of Lateral Dimension

Organometal halide perovskites become important in the photovoltaic and light emitting devices due to the compositional flexibility with AMX 3 formula (A is a monovalent organic ammonium cation; M is a metal ion; X is a halogen atom), imposing a significant demand to develop a synthetic route toward new types of nanocrystals. Although chemical pathways for perovskites nanoparticles were developed on the basis of the reprecipitation method, poor control of the nucleation and growth process results in a large size polydispersity that induces the ambiguities associated with a quantum confinement effect depending on their size. Here, a modified reprecipitation method is presented for the synthesis of CH 3 NH 3 PbBr 3 perovskite nanoparticles with a controlled nanoparticle size by systematically tuning the feed ratio of the precursors. Fine control of the nanocrystal size provides new insights into the quantum confinement effect observed in microscale and nanoscale perovskite materials, where their energy bandgap is associated with the thickness of nanoparticles and invariant to preferential growth in a lateral dimension.