To gain in-depth insights into the decay process of the excited states, transient absorption (TA) spectra of these materials are measured in toluene solutions. Under 355 nm pulsed laser excitation, a stimulated emission (SE) signal appears in the range of 400-650 nm. In comparison with the TA spectra measured before bubbling nitrogen, a new emission peak is observed at 515 nm at 30 ns after bubbling nitrogen, by which the quenching of triplet states by oxygen is alleviated (Figs. 3e, 3f and Supplementary Figs. 22, 23). Besides, from 400 to 600 nm, there are no obvious emission peaks of CCO-α, CBP-α and SXAC, indicating that the SE signals do not stem from the LE emission (Supplementary Figs. 24, 25). Therefore, the peak at 515 nm is assigned to delayed fluorescence, and the peak at about 440 nm belongs to prompt fluorescence. The temporal dynamics feature of prompt and delayed fluorescence peaks is presented in Supplementary Information. The delayed fluorescence of CCO-1 maintains a high intensity at 30-100 ns, on account of the continuous up-conversion of triplet states to singlet states, while the delayed fluorescence intensity of CBP-1 decreases sharply, suggesting there are not enough triplet states to replenish the singlet states to undergo rapid deexcitation. Furthermore, CCO-1 and CBP-1 have long-lived excited state absorption (ESA) signals at 500-750 nm after bubbling nitrogen (Fig. ). The lifetimes of this state are fitted to be 1.59 and 5.53 μs for CCO-1 and CBP-1, respectively, at the maximum absorption peaks, which are close to their τDFs measured by the transient PL decay spectra (1.64 and 4.35 μs for CCO-1 and CBP-1, respectively) (Supplementary Fig. ). So, these ESA signals can be assigned to the absorption of triplet states participated in RISC process. The absorption signal intensity of CCO-1 declines apparently at 500 ns, indicating a large number of triplet states have been converted to singlet states in this time scale, while considerable absorption signal intensity of CBP-1 remains until 2000 ns (Fig. ). These findings further validate that CCO-1 has a faster RISC process than CBP-1.