Behavior of an ideal injecting contact on a trap-free polymer

Solution coatable insulators capable of unipolar photoinjected carrier transport with negligible loss of transiting charge to deep traps are required for the fabrication of organic electrophotographic receptors. Molecularly designed polymeric insulators with these characteristics can now be routinely synthesized. Such trap-free polymer films provide a unique venue for the study of contact and interface behavior. A test for distinguishing ohmic from emission limited contact behavior which exploits the availability of these polymers is described. The test involves direct comparison of dark injection transients excited by application of a voltage step to the contact under investigation, with small signal time-of-flight transients photoexcited by laser pulse irradiation through a semitransparent blocking contact on the opposite face of the same specimen film.