Transient photoconductivity and charge generation in thin films of π-conjugated polymers

Transient photocurrents in thin films of methyl-substituted poly-phenylene (MeLPPP) and in phenyl-substituted poly-phenylenevinylene-type copolymer (PhPPV) were observed upon excitation by a laser flash. The questions on the origin of the optical charge generation and following charge transport in these materials are addressed. It has been argued that the observed current transient is a convolution of time-dependent charge carrier generation and their motion. By comparing the field-dependent photogeneration yield in MeLPPP and PhPPV, transient absorption and double shot photogeneration, the rate-limiting steps for photoionization in studied polymers were identified.