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 CsPbBr₃ 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 CsPbBr₃ nanocrystals. This work reveals a new understanding of the role of Cs⁺ cations, which take the A-site in ABX₃ perovskite and provide a new way to improve the performance of perovskites and their practical devices further.