Harnessing Hot Phonon Bottleneck in Metal Halide Perovskite Nanocrystals via Interfacial Electron-Phonon Coupling.

Slow hot carrier (HC) cooling resulting from hot phonon bottleneck has been widely demonstrated in metal halide perovskites. Although manipulating HC kinetics in these materials is of both fundamental and technological importance, this task remains a daunting challenge. Here, via interfacial engineering, i.e., epitaxial growth of Cs4PbBr6 on CsPbBr3 nanocrystals (NCs), we have revealed an obvious shortening of HC cooling times, evidenced by transient absorption and ultrafast PL spectra. Collaborated with the longitudinal optical (LO) phonon model, theoretical calculations verify the breaking of the hot phonon bottleneck in CsPbBr3@Cs4PbBr6 and identify the interfacial electron-LO phonon coupling as the leading mechanism for the observed large tuning of HC cooling times. Especially, the participation of LO phonons from Cs4PbBr6 enables the efficient Klemens channel for hot phonon decay. Our findings establish an effective method to tailor HC dynamics in perovskite NCs, which could be conducive to improving the performance of optoelectronic applications.