Extrinsic Carrier Photogeneration in Poly(N-vinylcarbazole) Films Doped with Dimethyl Terephthalate

Based upon the previously reported experimental results that the exciplex fluorescence of poly (N-vinylcarbazole) films doped with dimethyl terephthalate is partly quenched by an electric field, a model is proposed for the extrinsic carrier photogeneration mechanism. Interaction between a migrating singlet exciton and an electron acceptor (“encounter complex”) produces an electron-hole ion pair having a rather large separation through a charge-transfer process between the components and a thermalization process of the excess energy. This ion pair dissociates into free carriers with Onsager’s probability of escaping the geminate recombination which gives a “relaxed fluorescent exciplex state”. The field dependence of the initial separation of the ion pair is also discussed.