Hole mobilities in films of a pyrazoline:polycarbonate molecularly doped polymer

The hole mobilities of solution cast 1-phenyl-3-p-diethylaminostyryl-5-p- diethylphenyl-pyrazoline (DEASP) thin films have been characterized by the time-of-flight technique. The mobilities were measured for DEASP doping concentrations in the range 1090 % over a wide range of temperatures and electric fields, including measurements above the glass transition temperature Tg, and analyzed with use of recently suggested deconvolution procedures. The independence of the activation energy on the calculated distance between DEASP molecules and the exponential dependence of on suggest nonadiabatic small-polaron hopping is occurring, as was concluded for the molecularly doped polymer hydrazone. The decrease in activation energy above the glass transition temperature is clear evidence of the role of the polymer matrix in determining the activation energy. The electric-field dependence of while similar to previous measurements, i.e., lnE, provides significant new information. We report the first characterization of the field dependence of above the glass transition temperature: It appears to be unaffected by Tg, in contrast to the behavior of the activation energy. We also report the first observation of a mobility that decreases as the electric field increases at 10% DEASP concentration above 370 K. This result is contrary to the predictions of several investigators, but consistent with empirical equations suggested earlier. © 1990 The American Physical Society.