Electronic Transport in Organic Electrophotographic Receptors

ABSTRACTAll organic photoreceptors are now widely deployed in electrophotographic copiers and printers and represent the most important and commercially successful application of electronic organic materials. The need to optimize polymers for this application has stimulated fundamental investigations of charge generation, injection and transport processes in the disordered organic solid state. Electronic transport in a wide variety of glassy polymeric insulators has been studied by the time of flight drift mobility technique. It is typically found to proceed by a field driven chain of thermally activated tunneling events among active, compositionally identical, but energetically inequivalent sites. The inequivalece of site energies is attributed to the combined effect of disorder and site relaxation. Polymeric systems which differ widely in composition and morphology are found to exhibit a remarkably recurrent pattern of features in their transport behavior. Theoretical attempts to account for these universal features have been frustrated by their inability to explain the sublinear field dependence of the drift mobility and its variation with temperature. The drift mobility of polymers can be systematically modified by doping. Doping studies have provided the design rules which enable the fabrication of trap free polymers. The latter are an absolute requirement in electrophotography.