The ionic lattice of metal-halide perovskites is a deterministic component of their photophysical behaviour . The lattice dynamics are mostly driven by multiple optical phonons in the 1-10-meV energy range, and acoustic phonon modes at energies < 2 meV 2 . The optical phonons, in particular, have been identified to play a critical role in the electronic dynamics via strong polaronic coupling mechanisms . The consequences of the strong phonon in-