Charge Carrier Generation and Transport in Polyvinylcarbazole: A Model System for Polymeric Photoconductors

The problem of electron‐hole separation in polyvinylcarbazole (PVK) is discussed, based on new “time of flight” data, covering a time range from 10 nanoseconds to about 10 minutes. The experimental data are analyzed with the aid of the Onsager‐theory of electron‐hole recombination and yield an Onsager radius r0 of 18 ± 2 Å. Due to the high sensivity of the method it is possible to reproduce the low field regime of the Onsager recombination scheme. There are still sizeable deviations between the theoretical and the experimental quantum yields in the mid field regime. These differences do not enter into the determination of the r,‐value to a great extent because ro shows a weak logarithmic dependence on the extrapolated low and high field values of the charge carrier yields. The discrepancies between theory and experiment are believed to be caused by inhomogeneous electrical fields due to localized space charges in the zone of charge generation; they may in future provide information about the magnitude of “internal fields”.