Hopping charge transport in disordered organic materials: where is the disorder?

TL;DR

This paper reexamines how energetic disorder affects charge transport in organic materials, introducing a reliable method to calculate disorder parameters and explaining the disorder's impact on mobility temperature dependence.

Contribution

It presents a new method for directly calculating dipolar disorder magnitude from current transients in polar organic materials.

Findings

Calculated dipolar disorder parameters align with theoretical predictions.

Concentration dependence of disorder matches expected theoretical trends.

Proposed explanation for disorder's influence on mobility temperature dependence.

Abstract

Effect of energetic disorder on charge carrier transport in organic materials has been reexamined. A reliable method for mobility calculation and subsequent evaluation of relevant disorder parameters has been discussed. This method is well suited for a direct calculation of the magnitude of dipolar disorder $\sigma_\textrm{dip}$ in polar organic materials from the current transients. Calculation of $\sigma_\textrm{dip}$ for several transport materials with varying concentration of polar dopants gives concentration dependences that are in reasonable agreement with theoretical predictions. A possible solution of the puzzle concerning the disorder effect on the mobility temperature dependence has been suggested.