Carrier heating in disordered organic semiconductors

Abstract

We propose a semi-implicit model for hopping transport in disordered media with application to organic semiconductors. The results show excellent agreement with both Monte Carlo and standard master-equation calculations. In organic LEDs the applied field would result in heating of the charge carrier population by up to 100 °C above the lattice temperature and is more effective at lower temperatures. We show that the voltage dependence of the mobility in space charge limited LEDs is largely due to carrier heating and not to the previously considered charge density or barrier lowering effects. At the end we look into the effect of accounting for the soft nature of organic materials via the inclusion of polaronic rate binding energy and we find that carrier heating is suppressed at polaron binding energies above 0.1 eV.