Multi-peak single object emission of MAPbBr3 nanoplatelets synthesised using a non-template ligand-assisted reprecipitation route

Abstract

We report a modified non-template ligand-assisted reprecipitation synthesis of colloidal methylammonium lead bromide (MAPbBr₃) perovskite nanoplatelets (NPLs). The room-temperature process yields highly monodisperse, square-shaped NPLs that are stabilised by oleic acid and n-octylammonium bromide surface ligands. Scanning transmission electron microscopy (STEM) confirms the ultrathin square-shaped morphology of the synthesised NPLs with lateral dimensions of 17–20 nm. X-ray diffraction (XRD) reveals a cubic perovskite phase (Pmm) with a strong (100) orientation, and MicroStructure fitting reveals the contribution from two crystallite sizes of 18.3 nm and 117.9 nm. Small-angle X-ray scattering (SAXS) data, when fitted using a Guinier–Porod function, confirms the quasi-2D confinement of the NPLs, supporting the morphology observed in STEM analysis. Further fitting using a lamellar model reveals a thickness of 13.5 nm. 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%, a single-exponential PL decay time of 11.9 ns, and an optical band-gap of 2.3 eV derived from the 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 and laser-assisted photoactivation. 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.