Frohlich interaction dominated by a single phonon mode in CsPbBr₃

Electron-phonon interaction is essential for understanding electronic and optical properties of lead halide perovskites. Here, using multiphonon Raman scattering and THz time-domain spectroscopy, the authors characterize the full phonon spectrum of CsPbBr3 and identify a single phonon mode that dominates electron-phonon scattering. The excellent optoelectronic performance of lead halide perovskites has generated great interest in their fundamental properties. The polar nature of the perovskite lattice means that electron-lattice coupling is governed by the Frohlich interaction. Still, considerable ambiguity exists regarding the phonon modes that participate in this crucial mechanism. Here, we use multiphonon Raman scattering and THz time-domain spectroscopy to investigate Frohlich coupling in CsPbBr3. We identify a longitudinal optical phonon mode that dominates the interaction, and surmise that this mode effectively defines exciton-phonon scattering in CsPbBr3, and possibly similar materials. It is additionally revealed that the observed strength of the Frohlich interaction is significantly higher than the expected intrinsic value for CsPbBr3, and is likely enhanced by carrier localization in the colloidal perovskite nanocrystals. Our experiments also unearthed a dipole-related dielectric relaxation mechanism which may impact transport properties.