We report a modified non-template ligand-assisted reprecipitation (LARP) synthesis of colloidal methylammonium lead bromide (MAPbBr₃) perovskite nanoplatelets (NPLs). The room-temperature process yields highly monodisperse, square-shaped NPLs with lateral dimensions ranging from 10–15 nm, stabilised by oleic acid and n-octylammonium bromide surface ligands. Scanning transmission electron microscopy (STEM) confirms the ultrathin square-shaped morphology, while grazing-incidence X-ray diffraction (GI-XRD) reveals a cubic perovskite phase (Pm-3m) with a strong (100) orientation and an average crystallite size of 16.25 nm. Small-angle X-ray scattering (SAXS) data fitted using a Guinier-Porod function reveals a radius of gyration of 122.8 Å, and a dimension variable indicating quasi-2D confinement and corroborating the morphology obtained from STEM analysis. Ensemble optical spectroscopy exhibits a sharp photoluminescence emission (PLE) peak at 518 nm with a narrow peak-width of 26 nm, a quantum yield of ~50%, and an optical bandgap of 2.33 eV derived from Tauc analysis of the UV-Visible absorption spectrum. Single-dot spectroscopy reveals pronounced multi-peak emission behaviour, caused by quantum confinement effects promoted by atmospheric oxygen. This work provides a reproducible route to high-quality MAPbBr₃ NPLs, with properties ideal for optoelectronic and quantum photonic applications like perovskite-based LEDs and ultrathin photodetectors.

Keywords: MAPbBr3, perovskite, single particle spectroscopy

*corresponding author: e-mail: suhaas96@gmail.com