PHOTOGENERATION AND PHOTOLUMINESCENCE STUDIES IN BILAYER STRUCTURES CONTAINING POLY(P-PHENYLENE VINYLENE) AND MOLECULARLY DOPED POLYMERS

The photogeneration efficiency for photocarriers (holes and electrons) in poly(p-phenylene vinylene) (PPV) is measured in the presence of hi gh electric fields, for bilayer sandwich devices containing molecularl y doped polymers (MDP) and PPV. A hole transport diamine molecule (TPD ) and an electron transport malononitrile molecule (BCFM) each dispers ed in polycarbonate were used to study holes and electrons respectivel y. By performing photoluminescence (PL) experiments in the bilayer str uctures and hole collection experiments in single layers without the T PD:PC overcoat, we have concluded that generation of photocarriers in PPV is mainly a bulk mediated process, assisted by the applied electri c field, and not sensitized by the presence of the MDP. The electric f ield dependence of photogeneration suggests that photoexcitation resul ts in a strongly correlated electron-hole pair dissociated by the elec tric field.