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 CsPbBr3nanocrystals 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 CsPbBr3nanocrystals. This work reveals a new understanding of the role of Cs+cations, which take the A–site in ABX3perovskite and provide a new way to improve the performance of perovskites and their practical devices further.