Phonon-Mediated and Weakly Size-Dependent Electron and Hole Cooling in CsPbBr<sub>3</sub> Nanocrystals Revealed by Atomistic Simulations and Ultrafast Spectroscopy.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32049539.
- Also identified by DOI 10.1021/acs.nanolett.9b05051 and PMC identifier 7997624.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
We combine state-of-the-art ultrafast photoluminescence and absorption spectroscopy and nonadiabatic molecular dynamics simulations to investigate charge-carrier cooling in CsPbBr<sub>3</sub> nanocrystals over a very broad size regime, from 0.8 to 12 nm. Contrary to the prevailing notion that polaron formation slows down charge-carrier cooling in lead-halide perovskites, no suppression of carrier cooling is observed in CsPbBr<sub>3</sub> nanocrystals except for a slow cooling (over ∼10 ps) of "warm" electrons in the vicinity (within ∼0.1 eV) of the conduction band edge. At higher excess energies, electrons and holes cool with similar rates, on the order of 1 eV ps<sup>-1</sup> carrier<sup>-1</sup>, increasing weakly with size. Our ab initio simulations suggest that cooling proceeds via fast phonon-mediated intraband transitions driven by strong and size-dependent electron-phonon coupling. The presented experimental and computational methods yield the spectrum of involved phonons and may guide the development of devices utilizing hot charge carriers.