Excited energy states in poly(p-phenylenevinylene)

We have studied electronic excited states in films of poly (p-phenylene vinylene) using picosecond transient and steady state (cw) photoinduced absorption (PA) and photoluminescence (PL) as well as their excitation spectra (ES). The ps transient PA spectrum consists of two PA bands both with the same transient dynamics, one band peaks at ˜0.5 eV and the other peaks at 1.7 eV; neither of them can be related to the cw PA bands. Since the transient PL decay is correlated with the transient decay of both PA bands up to 200 ps, we conclude that the photoexcitations for t < 200 ps are radiative singlet excitons; they relax in about 200 ps and the radiative quantum efficiency substantially decreases thereafter. From the ES spectra of the cw PA band ES we tentatively assign the important excited electronic states in PPV such as the mAg exciton and the continuum band.