A Strategy for Tuning Electron-Phonon Coupling and Carrier Cooling in Lead Halide Perovskite Nanocrystals.

Perovskites have been recognized as a class of promising materials for optoelectronic devices. We intentionally include excessive Cs + cations in precursors in the synthesis of perovskite CsPbBr 3 nanocrystals and investigate how the Cs + cations influence the lattice strain in these perovskite nanocrystals. Upon light illumination, the lattice strain due to the addition of alkali metal Cs + cations can be compensated by light-induced lattice expansion. When the Cs + cation in precursors is about 10% excessive, the electron-phonon coupling strength can be reduced by about 70%, and the carrier cooling can be slowed down about 3.5 times in lead halide perovskite CsPbBr 3 nanocrystals. This work reveals a new understanding of the role of Cs + cations, which take the A-site in ABX 3 perovskite and provide a new way to improve the performance of perovskites and their practical devices further.