Time of flight results for molecularly doped polymers revisited

We examine the published data concerning the shape of the current transients obtained by the time of flight (TOF) technique for molecularly doped polymers and polyvinylcarbazole (PVK) and compare it with the predictions from the existing theories of charge carrier transport in disordered organic solids. We show that TOF current shapes frequently run contrary to theoretical predictions. Plateau appearances on TOF curves may or may not mean the equilibration of the charge carrier transport. Using both TOF and TOF-2 (uniform generation of charge carriers) techniques we demonstrate that hole transport in polycarbonate doped with p-diethylaminobenzaldehyde-diphenylhydrazone (DEH) and in PVK is indeed dispersive despite the fact that samples of these polymers equipped with an a-Se generation layer produce TOF curves with a plateau