Factors influencing stimulated emission from poly(p-phenylenevinylene)

We report measurements of stimulated emission (SE) in films of poly(p-phenylenevinylene) (PPV). SE is observed in the region of the dw photoluminescence, using 3.8 eV excitation, and 25% gain was obtained when a PPV film was incorporated into a microcavity structure. We show that photo-oxidation greatly reduces the SE. We demonstrate that singlet polaron excitons form a high proportion of the initially photoexcited states in pristine PPV, and consider that at the excitation density used here (3 x 10(19) cm(-3)) the fast decay of the SE is largely due to exciton-exciton annihilation.