HIGH-FIELD SATURATION OF CHARGE CARRIER DRIFT VELOCITIES IN ULTRAPURIFIED ORGANIC PHOTOCONDUCTORS

In ultrapurified single crystals of the organic photoconductors naphthalene, anthracene, and perylene time-of-flight charge carrier drift mobilities could be measured down to low temperatures, where p to 400 cm2/Vs were reached and sublinear velocity/field dependences observed, which set in at moderate fields (approximately 10 kV/cm) and display a tendency towards saturation of the drift velocity at almost-equal-to 10(6) cm/s at higher fields. Under the reasonable assumption that the (anisotropic and charge carrier sign-dependent) saturation velocities are caused by inelastic scattering under generation of the lowest optical phonon, anisotropic effective masses, mean free paths and scattering times can be estimated.