EXCITED ENERGY-STATES IN POLY(P-PHENYLENEVINYLENE)

We have studied electronic excited states in films of poly (p-phenylen e vinylene) using picosecond transient and steady state (cw) photoindu ced absorption (PA) and photoluminescence (PL) as well as their excita tion spectra (ES). The ps transient PA spectrum consists of two PA ban ds both with the same transient dynamics, one band peaks at similar to 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 th e transient decay of both PA bands up to 200 ps, we conclude that the photoexcitations for t < 200 ps-are radiative singlet excitons; they r elax in about 200 ps and the radiative quantum efficiency substantiall y decreases thereafter. From the ES spectra of the cw PA band ES we te ntatively assign the important excited electronic states in PPV such a s the mA(g) exciton and the continuum band.