Colloidal perovskite nanocrystals based on formamidinium lead halide (FAPbX 3 ) have been synthesized by the ligand-assisted reprecipitation method using PbX 2 − dimethyl sulfoxide complexes as precursors at room temperature. Well-defined cubic-shaped FAPbX 3 nanocrystals have been obtained with a size d of ∼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 nearinfrared region (λ 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.

In the past decade, lead halide perovskite nanocrystals or quantum dots (QDs) have attracted keen interest due to their potential applications in many optoelectronic systems. In addition, all-inorganic (CsPbX3) perovskite QDs are suggested to be efficient single photon emitting centers. Herein, we study the photon emission properties of recently synthesized organic–inorganic FAPbBr3 QDs. Our results show that individual FAPbBr3 QDs can act as good single-photon sources with very low multiphoton emission probability achieved by extremely fast nonradiative Auger recombination. However, they exhibit photodegradation and fluorescence intensity intermittency, called blinking. By analyzing the ON­(OFF) duration time distribution, particularly the OFF duration times, we suggest that two types of blinking (type-A and type-B) simultaneously contribute to the blinking behavior of FAPbBr3 QDs. In type-A and type-B blinking, the ON/OFF periods are attributed to charged/discharged states and to activation/deactivation of fast nonradiative recombination centers, respectively. By analyzing the ON/OFF duration cutoff time as a function of the excitation intensity, we verify that type-A blinking is caused mainly by diffusion-controlled electron transfer, partially accompanied by Auger ionization processes.

Perovskite nanoparticle composite films with capability of high-resolution patterning (≥2 µm) and excellent resistance to various aqueous and organic solvents are prepared by in situ photosynthesis of acrylate polymers and formamidinium lead halide (FAPbX ) nanoparticles. Both positive- and negative-tone patterns of FAPbX nanoparticles are created by controlling the size exclusive flow of nanoparticles in polymer networks. The position of nanoparticles is spatially controlled in both lateral and vertical directions. The composite films show high photoluminescence quantum yield (up to 44%) and broad color tunability in visible region (λ = 465-630 nm).