Studies of transient stimulated emission in DOO-PPV films

We experimentally and theoretically investigated the stimulated emission ba nd in neatly prepared 2,5-dioctyloxy poly(p-phenylene vinylene) (DOO-PPV) f ilms. We found that at moderately high excitation intensity spectral narrow ing (SN) occurs due to the amplified spontaneous emission (ASE). A complex ASE build-up and decay dynamics as a function of excitation intensity and s tripe length is observed. We also found that the exciton energy relaxation process within the inhomogenously broadened energy distribution becomes fas ter when ASE occurs. A theoretical model taking into account the polymer fi lm gain and loss, the propagation effect and the time dependent exciton gen eration process is developed and used to explain the experimental data. (C) 2001 Published by Elsevier Science B.V.