Fig. 5. Transient absorption (TA) spectra of BODIQU-tBuCZ solution before and after protonation. (a) Pseudo-color TA spectra of BODIQU-tBuCZ. (b) TA spectra at different time delays for BODIQU-tBuCZ, with insets showing energy levels and optical transitions. (c) Comparison of photo-induced absorption (PIA) peak decay dynamics before and after protonation. (d) Pseudo-color TA spectra of BODIQU-tBuCZ-H⁺. (e) TA spectra at different time delays for BODIQU-tBuCZ-H⁺, with insets illustrating energy levels and optical transitions in the proposed polaron model. (f) Comparison of P2 and PIA peak decay dynamics in BODIQU-tBuCZ-H⁺.