Room-Temperature Synthesis of Widely Tunable Formamidinium Lead Halide Perovskite Nanocrystals

Colloidal perovskite nanocrystals based on formamidinium lead halide (FAPbX3) have been synthesized by the ligand-assisted reprecipitation method using PbX2–dimethyl sulfoxide complexes as precursors at room temperature. Well-defined cubic-shaped FAPbX3 nanocrystals have been obtained with a size d of ∼10 nm. The synthesized FAPbX3 nanocrystals show bright photoluminescence with a high photoluminescence quantum yield (75% for FAPbBr3). The lifetimes of FAPbBr3 nanocrystals were measured for the samples isolated at several different centrifugal speeds. The photoluminescence can be tuned from the blue to near-infrared region (λpeak = 408–784 nm) by changing either the amount of oleylamine or the composition of X. The color expression range is 135% of the NTSC standard. The bandwidth of the photoluminescence spectra of FAPbX3 nanocrystals is narrow (full width at half-maximum of 18–48 nm). FAPbX3 nanocrystals show thermal stability that is better than that of MAPbBr3 nanocrystals.