CARRIER TRANSPORT IN VANDERWAALS SOLID .2. CARRIER TRANSPORT PHENOMENA IN 1,3-DIPHENYL-5-(PARA-CHLOROPHENYL)-2-PYROZOLINE

The hole drift mobilities in the different orientations of the single crystal of the title compound were measured by using the time-of-flight method. It was found that the mobility of 2 multiplied by 10** minus **2 cm**2/V. sec in the c-axis direction is slightly larger than other a* and b-axis directions at room temperature, and a significant change in activation energy was observed at 12 degree C only in the c-axis direction. The anisotropy in drift mobility and the change in activation energy was discussed in terms of the small polaron model. It has been shown that the drift mobilities in the glassy state previously reported can be also explained in terms of the modified small polaron model in the ″classical″ limit by introducing the ideas of the ″effective temperature″ and the Poole-Frenkel effect.