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

TL;DR

This study uses Monte-Carlo simulations within the dipolar glass model to accurately reproduce charge transport properties in doped polycarbonate, aligning well with experimental data without adjustable parameters.

Contribution

It provides the first self-consistent verification of the dipolar glass model for charge transport in a real molecular system, matching experimental results.

Findings

Simulated mobility shows Poole-Frenkel dependence matching experiments

Transients are universal and non-dispersive at room temperature

Transient decay follows a power law with exponent close to -2

Abstract

We present the results of Monte-Carlo simulations of the charge carrier transport in a disordered molecular system containing spatial and energetic disorders using the dipolar glass model. Model parameters of the material were chosen to fit a typical polar organic photoconductor polycarbonate doped with 30% of aromatic hydrazone, whose transport properties are well documented in literature. Simulated carrier mobility demonstrates a usual Poole-Frenkel field dependence and its slope is very close to the experimental value without using any adjustable parameter. At room temperature transients are universal with respect to the electric field and transport layer thickness. At the same time, carrier mobility does not depend on the layer thickness and transients develop a well-defined plateau where the current does not depend on time, thus demonstrating a non-dispersive transport regime. Tails of the transients decay as power law with the exponent close to -2. This particular feature indicates that transients are close to the boundary between dispersive and non-dispersive transport regimes. Shapes of the simulated transients are in very good agreement with the experimental ones. In summary, we provide a first verification of a self-consistency of the dipolar glass transport model, where major transport parameters, extracted from the experimental transport data, are then used in the transport simulation, and the resulting mobility field dependence and transients are in very good agreement with the initial experimental data.