Transient photoconductivity in a thin film of a poly-phenylenevinylene-type conjugated polymer

Abstract

Transient photocurrents in a 150 nm thick film of a copolymer of a phenyl-substituted poly-phenylenevinylene were observed upon excitation by a 10 ns laser flash. The signal is due to a superposition of time-dependent generation of mobile holes and their motion. The essential quantity considered was the number of holes transported in either the neat sample or a film doped with trinitrofluorene as a function of electric field, temperature, photon dose at different photon energies, and polarity of the irradiated electrode. Based upon complementary spectroscopic evidence it has been argued that the rate limiting step for charge generation is the dissociation of geminate pairs forming an electron at an either unintentional or intentional electron acceptor and hole at an adjacent chain. The field and temperature dependence can be fitted by a recent theory by Arkhipov et al. that differs from the conventional Onsager description.