High Photoluminescence Quantum Yield (>95%) of MAPbBr3 Nanocrystals via Reprecipitation from Methylamine-MAPbBr3 Liquid

Ligand-assisted reprecipitation strategy (LARS) is one of the most popular methods for the fabrication of lead halide perovskite nanocrystals; however, it has always been criticized for poor repeatability and low stability of the resulting nanocrystals. Herein, we demonstrate that liquefying MAPbBr3 single crystals via methylamine (MA) gas rather than being dissolved in N,N-dimethylformamide (DMF) are more beneficial in synthesizing high-quality and stable MAPbX3 (X = Cl, Br, I) based on the LARS. In particular, the liquefied single-crystal-derived MAPbBr3 nanocrystals show a high PLQY exceeding 95%, while 87% for the one derived from the traditional LARS. It is found that replacing DMF solvent with MA gas can not only passivate the MA vacancy defects on the nanocrystal surface but also hinder the formation of halide vacancies, both of which significantly enhance the stability. Benefitting from the impressive PLQY and high X-ray attenuation, MAPbBr3 nanocrystals exhibit strong radioluminescence under X-ray excitation, which further enables their application in large-area X-ray imaging. Furthermore, liquefied perovskite single crystals can be further applied in the in situ synthesis of MAPbX3 nanocrystals within the mesoporous SiO2 template, affording the MAPbX3@SiO2 complex, which exhibits potential as stable solid-state light-emitting diodes.