Fig. 3. Differential transmission spectra of (PEA)₂SnI₄ upon (a and b) resonant excitation (E_pump = 1.96 eV) of the lowest lying excitonic states (c and d) non-resonant excitation of hot free carriers (E_pump = 3.1 eV). The DT signal both in the (a and c) X_LE and (b and d) X_HE regions is normalized to the maximum in X_LE. As a reference, the steady-state absorbance spectrum is shown as a red dashed line. All experiments were performed at 77 K with a pump intensity of 350 μW cm⁻².