Electron phonon coupling and coherent phonon modulation of charge transfer in two dimensional perovskite (AE2T)₂AgBiI₈

Two-dimensional (2D) hybrid organic inorganic perovskites (HOIPs) possess quantum-well-like atomic structures with alternating organic and inorganic layers, and exhibit well-separated organic and inorganic energy levels near the band edges. The 2D HOIP (AE2T)₂AgBiI₈ (AE2T: 5,5'-diylbis(amino-ethyl)-(2,2'-biothiophene)) has a type 2B electronic structure in which the valence band maximum (VBM) dominated by the organic components, lies in close proximity to the highest occupied inorganic-derived states. Here, we show how electron-phonon coupling effects can modulate the inorganic and organic derived band levels, which may induce charge transfer between organic and inorganic components. Transient absorption spectra (TAS) measured for (AE2T)₂AgBiI₈ shows a carrier population oscillation at ~114 cm^-1. Electron phonon coupling effect calculations for 48 phonon modes from 95 to 125 cm^-1 show that electron phonon coupling strength has a single largest peak near 115 cm^-1,  very close to the observed TAS oscillation frequency. We thus demonstrated a striking example of how electron-phonon interactions can be used to manipulate important charge and energy transfer processes in 2D HOIPs.