Synthesis and Spectroscopy of Monodispersed, Quantum-Confined FAPbBr₃ Perovskite Nanocrystals

Novel phenomena emerge as the sizes of semiconductor nanocrystals (NCs) are tuned into the quantum confinement regime, such as size-dependent optical gaps, enhanced exciton–exciton interactions, and modified hot carrier relaxation dynamics. As such, it is interesting to synthesize and study quantum-confined NCs of the recently intensively studied lead halide perovskite NCs for many emerging applications. Here we report on the synthesis of monodispersed, quantum-confined organic–inorganic hybrid perovskite NCs, formamidinium lead bromide (FAPbBr3), in the size range of 3.1–7.7 nm with their emission wavelength tunable from 474 to 521 nm. We study the hot carrier relaxation and multiexciton Auger recombination dynamics of these NCs which are benchmarked against all-inorganic CsPbBr3 NCs and traditional CdSe and PbSe NCs. We find that the motion of the large organic cations (FA) strongly accelerates hot carrier relaxation and breaks the “phonon bottleneck” expected for strongly confined NCs, whereas its influence on multiexciton Auger recombination is only minor.