Adiabatic and non-adiabatic small polaron hopping in molecularly doped polymers

Abstract

New hole drift mobility measurements for the molecularly doped polymer DEH ( p-diethylaminobenzaldehyde-diphenyl hydrazone) in polycarbonate and literature data for TPD (N,N′-diphenyl-N,N′-bis (3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine) in polycarbonate are analyzed by a new procedure which separates the functional dependence of the mobility on temperature and molecular spacing ϱ. Our analysis indicates that the dependence of the mobility on ϱ arises from different sources. In DEH: polycarbonate it is due to an overlap integral, as normally expected. In TPD: polycarbonate it is due entirely to the dependence of the activation energy on p, a significant clue to the underlying microscopic hole hopping mechanism. These data are consistent with the small polaron hopping theory in two regimes, non-adiabatic hopping in DEH:polycarbonate and adiabatic hopping in TPD: polycarbonate.