Fig. 3: Transient absorption spectroscopy at 77 K.

a, b Transient absorption maps of BA2FAPbI7 following photoexcitation at 2.17 eV (a) and 2.43 eV (b) at 77 K. c, d Residual kinetics after subtracting a multi-exponent fit from the TA kinetics under pump energy of (c) 2.17 eV and (d) 2.43 eV, that were obtained by integrating around 2.15 eV.