The Role of\nCations in Coherent Phonon Properties\nin Dion–Jacobson Type 2D Hybrid Organic–Inorganic Perovskites

2D hybrid organic–inorganic perovskites (HOIPs)\nhave great\nprospects in new-generation photovoltaic and luminescence applications.\nThe complex interaction between exciton and lattice motions plays\nan important role in determining the exciton properties of 2D HOIPs.\nHowever, the exploration of the regulation mechanism of phonons and\nthe exciton–phonon (ex–ph) interaction is still very\nlimited, especially for Dion-Jacobson (DJ) type 2D HOIPs. Here, we\ninvestigate three DJ-type 2D HOIPs with different cations, (3AMP)PbI<sub>4</sub>, (4AMP)PbI<sub>4</sub>, and (1,6-HDA)PbI<sub>4</sub>, using\ntemperature-dependent steady-state spectra and time-resolved spectra.\nIt is found that the subtle difference of functional group position\nin cations and the difference between ring and straight carbon chains\nhave a profound effect on the structural distortion, the ex–ph\ncoupling strength, and even the band gap variation trend with temperature\nin the DJ type 2D HOIP system. The study provides new insights into\nhow to manipulate ex–ph interactions by targeting ligand modifications\nto 2D perovskite structures.