Extrinsic carrier photogeneration in poly-<i>N</i>-vinylcarbazole. III. CT fluorescence quenching by an electric field

Abstract

Field-induced CT fluorescence quenching has been observed in a poly-N-vinylcarbazole (PVCz) film doped with 1,2,4,5-tetracyanobenzene, which exhibits a large sensitized photocurrent in the corresponding CT absorption region. The CT fluorescence quenching is attributed to carrier photogeneration by the ’’field-assisted thermal dissociation’’ of an ion pair which has a higher excited CT state as precursor. The Onsager model for the dissociation of an ion pair satisfactorily explains the experimental data of the field and temperature dependences of the fluorescence quenching by an electric field. Combining previously proposed mechanism of extrinsic carrier photogeneration in the exciplex systems, a more general mechanism has been presented for extrinsic carrier photogeneration in solid-state, excited donor–acceptor systems.