Verification of the dispersive charge transport in a hydrazone:polycarbonate molecularly doped polymer

Abstract

We report results of specially planned experiments intended to verify the dispersive character of the charge carrier transport in polycarbonate molecularly doped with hydrazone at 30 wt% loading, using for this purpose samples specifically featuring a well-defined plateau on a linear-linear plot. For this purpose we propose a new variant of the time-of-flight technique which allows easy changing of the generation zone width from about 0.5 µm (surface excitation) through intermediate values to full sample thickness (bulk excitation). To achieve this, we use electron pulses of 3-50 keV energy rather than traditional light pulses provided by lasers. Experimental results corroborated by numerical calculations uniquely prove that carrier transport in this molecularly doped polymer is dispersive, with the dispersion parameter equal to 0.75. Nevertheless, the mobility field dependence follows the famous Poole-Frenkel law.

Charge carrier transport in molecularly doped polycarbonate as a test case for the dipolar glass model

“…In this simulation the magnitude of the slope of the mobility dependence is directly dictated by the magnitude of the dipolar disorder. Hence, the good agreement between our simulation and the experiment 21,23,33 provides an addition support in favor of the existence of correlated energetic disorder with σ ≃ 0.1 eV in organic materials. At the same time, as it was stressed in Ref.…”

“…In this paper we present the result of such test for the particular set of transport parameters, extracted from the experimental mobility data for a typical organic semiconducting glass containing 30% (by weight) hole transporting aromatic hydrazone DEH in polycarbonate (PC) matrix, and then compared our results with the experimental ones. [19][20][21][22][23] Experimental results, provided in different papers, agree well, thus justifying our choice of the reference transport material.…”

Hole transport in polystyrene and polycarbonate doped with polar dopants

“…For curve 1, this region is much shorter: ≈0.7 orders of magnitude. A similar flight picture is intrinsic for dispersion transport at a dispersion parameter of = 0.75 [6]. Close time dependences of transient current are recorded for 70% DEASP-PS as well (Fig.…”

“…4) is strongly nonequilibrium: even farther from quasi equilibrium than 30% DEH-PC is [4,6,9]. Note that there is an unusually slow current decay after flight…”

“…In PC doped with polar molecules of p diethylami nobenzaldehyde diphenylhydrazone (DEH) with a dipole moment of 3.16 D, the hole transport is non equilibrium [3][4][5][6]. Note that a flat plateau is often observed on time of flight curves, a phenomenon that is considered evidence for the achievement of quasi equilibrium transport in the system.…”