Charge Trapping in Molecularly Doped Polymers

Hole mobilities have been measured in di-p-tolylphenylamine doped poly(styrene) containing p-diethylaminobenzaldehyde diphenylhydrazone (DEH), an 0.32 eV trap. A DEH molar concentration of 10-5 decreases the mobility by a factor of two. For concentrations in excess of 10-5, the mobilities decrease with increasing concentration as approximately c-1.4, the field and temperature dependencies remaining essentially unchanged. For concentrations in excess of 10-1, transport is dominated by trap-to-trap hopping and the mobility increases with increasing trap concentration. The results are discussed within the framework of the Hoesterey-Letson formalism and the recent simulations of Wolf et al.. and Borsenberger et al..