Phonon modes and exciton-phonon interactions in CsPbCl3 single nanocrystals

Micro-photoluminescence measurements have been performed on single cubic-shaped CsPbCl3 nanocrystals (NCs) with side lengths of nearly twice the Bohr diameter, i.e. in the intermediate confinement regime. We observed two peaks, linearly polarized and spectrally separated by 1-3 meV associated to the bright states of the exciton fine structure. We took advantage of these emission polarization properties to track the energy and the linewidth broadening of individual peaks with increasing temperature. Two regimes exist in the broadening of emission peaks, at low and high temperature, dominated respectively by acoustic or longitudinal optical phonons couplings. We deduce the respective strengths of the interactions. We also measured micro-Raman spectra of an ensemble of CsPbCl3 NCs. The energy of the mean optical phonon responsible for the high temperature broadening of the emission peaks is in good agreement with the highlighted longitudinal phonon modes observed in the Raman spectra. Finally, we compare our results to previous experimental works done on other lead halide perovskites emitting at lower energy.

Automated summary

Micro-photoluminescence measurements were conducted on single cubic-shaped CsPbCl3 nanocrystals (NCs) in the intermediate confinement regime. Two polarized and spectrally separated peaks, associated with bright states of the exciton fine structure, were observed. The energy and linewidth broadening of the peaks at increasing temperature revealed two regimes dominated by different phonon couplings. Raman spectra analysis provided further insight into the longitudinal phonon modes and confirmed the temperature-dependent broadening.