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

Colloidal perovskite nanocrystals based on formamidinium lead halide (FAPbX(3)) have been synthesized by the ligand-assisted reprecipitation method using PbX2-dimethyl sulfoxide complexes as precursors at room temperature. Well-defined cubicshaped FAPbX(3) nanocrystals have been obtained with a size d of similar to 10 nm. The synthesized FAPbX(3) nanocrystals show bright photoluminescence with a high photoluminescence quantum yield (75% for FAPbBr(3)). The lifetimes of FAPbBr(3) nanocrystals were measured for the samples isolated at several different centrifugal speeds. The photoluminescence can be tuned from the blue to near infrared region (lambda(peak) = 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 FAPbX(3) nanocrystals is narrow (full width at half-maximum of 18-48 nm). FAPbX(3) nanocrystals show thermal stability that is better than that of MAPbBr(3) nanocrystals.