Fig. 3. Kinetics and intraband relaxation in 2D Dion–Jacobson perovskites.

Normalized transient absorption kinetics (a) probed at a wavelength of 554 nm for the (3AMP)PbI₄ film (excitation at 330 nm) and (b) probed at a wavelength of 518 nm for the (4AMP)PbI₄ film (excitation at 316 nm), with different pump fluences of 0.8 μJ/cm², 2.0 μJ/cm², and 4.0 μJ/cm². The solid lines show best fits to the experimental data with an exponential function. Time evolution of hot electron relaxation (c) starting from CBM + 7 for (3AMP)PbI₄ (excess energy = 1.52 eV) and (d) starting from CBM + 4 for (4AMP)PbI₄ (excess energy = 1.38 eV). Inserts show the electronic energy levels of (3AMP)PbI₄ and (4AMP)PbI₄ at the high-symmetry Γ-point and B-point, respectively, involved in the nonadiabatic molecular dynamics calculations (NAMD). Vibrational modes responsible for the intraband relaxation in (e) (3AMP)PbI₄ and (f) (4AMP)PbI₄ (the vibrational motions of the organic cations are omitted). The DFT and NAMD calculations were performed at the GGA/PBE level with SOC.