With the validated kinetic model, we proceed to determine the 𝑘 1 and 𝑘 3 from the spectra results. There is a negligible excited state absorption signal in the tr-ESFG which indicates no or little population of trion in the measured time window, i.e. , 𝛥[𝑇] ≈ 0, suggesting that 𝑘 1 is negligible comparing to k 3 . Thus, 𝑘 3 -1 ≈ (𝑘 1 + 𝑘 3 ) -1 = 5.6 𝑝𝑠.The formation of CT-trion dominates the exciton relaxation and quenches the original trion formation.