TA spectroscopy TA spectra were measured by the pump-probe method . For a probe pulse, we generated a white light pulse by focusing the signal light (1200 nm) from another OPA (Light Conversion, TOPAS-Prime) on a sapphire crystal (3 mm thickness). For the pump pulse, we employed one of the two pulses below accordingly depending on the measurement time range. In the picosecond range, we used the same excitation pulse as the steady-state PL spectroscopy (360 nm). In the nanosecond range, we used the third-harmonic (355 nm) of the output from a Nd:YAG laser (EKSPLA NT242, central wavelength: 1064 nm, pulse duration: 6 ns). The pump pulse fluences at the sample position were 0.34 mJ/cm 2 for picosecond measurements, 0.81 mJ/cm 2 (in toluene) and 1.63 mJ/cm 2 (in THF) for nanosecond measurements. The polarizations of the pump and probe pulses was set to the magic angle configulration (~54.7°). The probe pulse passed through the sample solution was dispersed by a polychromator (JASCO, CT-10, 300 grooves / 500 nm), and the spectra were recorded by a multichannel detection system with a CMOS sensor (UNISOKU, USP-PSMM-NP). The concentration of the sample solutions was prepared to be 0.1 mM. All measurements were conducted with N2 gas bubbling.