Charge Transport in Vapor-Deposited p-Diethylaminobenzaldehyde Diphenylhydrazone

Abstract

Hole mobilities of vapor-deposited p-diethylaminobenzaldehyde diphenylhydrazone glasses have been measured over a range of temperatures that includes the glass transition temperature Tg. Discontinuities in the temperature dependence were observed at Tg. For T > Tg, the activation energy is approximately 1/2 its value for T < Tg. The results are described within the framework of a formalism based on disorder, due to Bässler and coworkers. The formalism is based on the assumption that charge transport occurs by hopping through a manifold of localized states that are distributed in energy and distance. The key parameters of the formalism are σ, the energy width of the hopping site manifold, Σ the degree of positional disorder, and μ0 a prefactor mobility. For T < Tg, the results yield σ = 0.106 eV, μ0 = 4.6×10—3 cm2/Vs, and Σ = 1.0. Analyzing the data for T > Tg leads to the conclusion that σ increases with increasing temperature while Σ remains constant.