Time resolved studies of electronic transport in polymeric insulators

Transport in a wide variety of glassy polymeric insulators has been found to be characterized by a convoluted yet familiar pattern of electric field and temperature dependence below T_g, the glass transition temperature, and by a relatively abrupt change in temperature dependence near T_g. Though diverse, all of these glassy dielectrics share the feature that electronic transport is mediated by field-assisted thermally stimulated emission from localized states, a process which remains incompletely understood. By proper `molecular engineering´ it has become possible to design dielectric polymers which exhibit efficient and completely trap-free transport, a requisite feature for practical applications to electrophotography. The importance of the mechanistic understanding derived from analysis of time-resolved injection in the historical development of viable organic-polymer-based photoconductors is discussed. Three materials systems are described: (1) poly(N-vinylcarbazole), PVK; (2) molecularly doped polymers; and (3) polysilanes and polygermanes