Compositional engineering of the optical properties of hybrid organic-inorganic lead halide perovskites is one of the cornerstones for the realization of efficient solar cells and tailored light-emitting devices. We study the effect of compositional disorder on coherent exciton dynamics in a mixed FA0.9Cs0.1PbI2.8Br0.2 perovskite crystal using photon echo spectroscopy. We reveal that the homogeneous linewidth of excitons can be as narrow as 16μeV at a temperature of 1.5K. The corresponding exciton coherence time of T2=83ps is exceptionally long being attributed to the localization of excitons due to variation of composition at the scale of ten to hundreds of nanometers. From spectral and temperature dependences of the two- and three-pulse photon echo decay we conclude that for low-energy excitons, pure decoherence associated with elastic scattering on phonons is comparable with the exciton lifetime, while for excitons with higher energies, inelastic scattering to lower energy states via phonon emission dominates.
@article{arxiv.2305.09301,
title = {Long-lived exciton coherence in mixed-halide perovskite crystals},
author = {Stefan Grisard and Artur V. Trifonov and Ivan A. Solovev and Dmitri R. Yakovlev and Oleh Hordiichuk and Maksym V. Kovalenko and Manfred Bayer and Ilya A. Akimov},
journal= {arXiv preprint arXiv:2305.09301},
year = {2023}
}