SPATIALLY RESTRICTED DIFFUSION PROCESS OF PHOTOGENERATED HOLE IN POLY(N-VINYLCARBAZOLE) FILM AS REVEALED BY TRANSIENT ABSORPTION-SPECTROSCOPY

Charge recombination (CR) kinetics of photogenerated ionic species in poly(N-vinylcarbazole) (hereafter abbreviated as PVCz) film doped with an electron acceptor is investigated by transient absorption spectros copy in the submicrosecond to millisecond time regime. Characteristic initial concentration dependence of the CR kinetics is observed and is qualitatively explained by a spatially restricted hole-diffusion-cont rolled CR model. From the temperature dependence of CR kinetics combin ed with a charge transfer (CT) fluorescence decay measurement, it is c oncluded that a CR with a long-range electron-transfer mechanism occur s under low-temperature conditions. Applicability of a 3-D random walk model in an energy disordered lattice to the CR kinetics is examined by means of a Monte Carlo simulation technique, and it is found that t he spatial restriction condition is necessary to reproduce the CR kine tics in a PVCz film.