Electric field activated nonlinear and disorder-induced charge transport in doped polymer devices

摘要

In the present study, temperature dependent conductivity and field dependent nonlinear transport are adopted to provide insight into the charge transport in poly(3-methylthiophene) polymer thin film devices that are electropolymerized at different temperatures. The samples obtained at different temperature show relative disorder quantified by the conductivity ratio, σ_r = σ (84 K)/σ (300 K) which is further correlated with the morphology of the samples. Charge transport in each sample is governed by variable range hopping mechanism and the parameters like density of states at the Fermi level [N(E_F)], average hopping distance (R) and average hopping energy (W) have been estimated. Electric field activated nonlinear transport is described by multistep tunneling model of Glazman-Matveev (GM model) over four separate channels of conduction. It is concluded that the field dependent conductivity has a 'field-scale' in all the samples where the conductivity converges to a single master curve in the temperature range of observation. The results obtained from the conductivity ratio and temperature dependent conductivity are strongly supported by electric field dependent conductivity and nonlinear exponents.