Photogeneration in a ladder-type poly(para-phenylene)

Photogeneration of charge carriers in a methyl-substituted ladder-poly(para-phenylene) (LPPP), which possesses a high intrachain order, has been studied by xerographic experiments. The Time-of-Flight technique was used to study charge carrier transport in LPPP. The quantum efficiency of charge carrier generation was calculated by evaluating the photoinduced-discharge curves (PIDCs) and found to be independent of both excitation wavelength and temperature. The results can be described by a modified Braun theory with a simple exponential distribution of radii of thermalized electrons. LPPP shows a high charge carrier mobility up to 10(-3) cm(2)/V.s, a high primary quantum efficiency of 80%, a low residual potential and a small dark decay. Thus, LPPP represents a promising material to build single component single-layer photoreceptors. For a comparison, another polymer ladder-type poly(para-phenylene thienylene) LPPPT, which possesses low intrachain order, is also studied. The quantum efficiency of free charge generation in LPPPT is about one order of magnitude smaller as compared to that in LPPP.