Fig. 3
a Electronic band structures and b phonon band spectra obtained from the quasi-1D TMSGeI3 perovskite bulk structure calculated within PBEsol. For both electronic and vibrational DOS, we show the projections to Ge (red lines), I (green lines), and TMS (blue lines). In b, for clarity, high-frequency phonon modes (> 250 cm− 1) originating from (CH3)3 S+ ligands were omitted