Charge-transfer (CT) fluorescence of poly(N-vinylcarbazole) (PVCz) films doped with 1,2,4,5-tetracyanobenzene was investigated in comparison with exciplex (and/or exterplex) fluorescence of PVCz films doped with 1,4-dicyanobenzene by using the nanosecond time-correlated single-photon-counting method. For excitation of PVCz absorption band and CT absorption band, the fluorescence peak in the time-resolved spectra shifted continuously to short wavelength with time. The direction of the shift was opposite to that of the exterplex fluorescence. The dependence of the steady-state CT fluorescence intensity on concentration of the acceptor was also different from the exciplex system. These different behaviours of fluorescence dynamics between the CT and the exciplex systems were discussed from the viewpoint of the overlap of CT and exterplex fluorescence for the CT system and of a morphological change of PVCz films caused by formation of ground-state CT complexes.
- charge-transfer complex
- fluorescence dynamics