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AbstractPPV was sensitized by ethyl viologen which is well known as a good electron acceptor, to achieve efficient ionization of the excitons created by photoexcitation of PPV. PPV/ethyl-viologen composites were successfully prepared from PPV-precursor and ethyl-viologen because both compounds could be soluble in polar solvents such as methanol, water etc. We observed dramatic decrease of photoluminescence efficiency in the PPV/ethyl-viologen composite film as compared with PPV film. This is attributed to photoinduced electron transfer in PPV/ethyl-viologen composites and the efficient ionization of the excitons was occurred in this composite film. Time-resolved photoluminescence of composite films was also studied to obtain the information of this photoinduced electron transfer dynamics.

AbstractLight emitting properties of poly(2-fluoro-l,4-phenylenevinylene) (PFPV) were investigated by using steady-state and time-resolved photoluminescence spectroscopies, EL spectra and current-voltage characteristics. PFPV exhibited a red-shifted structureless emission with higher PL and EL quantum efficiency in comparison with PPV. The time-resolved PL experiments revealed that the shorter wavelength emission is attributable to the free excitons and the longer wavelength emission to the self-trapped excitons. The I-V characteristics of the polymers showed typical diode characteristics and the operating voltages of PPV and PFPV were 6 V and 10 V, respectively. The higher relative EL quantum efficiency of PFPV may be due to the higher PL quantum efficiency and the smaller band offset between the aluminum and the LUMO of the PFPV as compared with that of PPV.