Fig. 6: The second component (II) of the exciton relaxation kinetics.

a Normalized band-edge GSB relaxation process under the pump fluence of 2 µJ cm⁻² for the (PEA)₂SnI₄, (BA)₂SnI₄, (HA)₂SnI₄, and (OA)₂SnI₄ thin films. The internal illustration shows the relaxation process of the four materials within 2 ps. b Change in the lifetime of component II in the TA spectra of the (PEA)₂SnI₄ sample with temperature. c Band-edge exciton relaxation process of (PEA)₂SnI₄ (red represents) and PEAI-rich (blue represents) under the pump fluence of 2 µJ cm⁻². d Schematic diagram of the TA relaxation process with excitation at 520 nm. e Relationship between the lifetime (blue represents) of the Auger process and the pump fluence; the red curve is the fitting result of the two-body interaction theory of excitons.