Universal Arrhenius Temperature Activated Charge Transport in Diodes from Disordered Organic Semiconductors

Abstract

Charge transport models developed for disordered organic semiconductors predict a non-Arrhenius temperature dependence $\mathrm{ln}(\ensuremath{\mu})\ensuremath{\propto}1/{T}^{2}$ for the mobility $\ensuremath{\mu}$. We demonstrate that in space-charge limited diodes the hole mobility (${\ensuremath{\mu}}_{h}$) of a large variety of organic semiconductors shows a universal Arrhenius temperature dependence ${\ensuremath{\mu}}_{h}(T)={\ensuremath{\mu}}_{0}\mathrm{exp}(\ensuremath{-}\ensuremath{\Delta}/kT)$ at low fields, due to the presence of extrinsic carriers from the Ohmic contact. The transport in a range of organic semiconductors, with a variation in room temperature mobility of more than 6 orders of magnitude, is characterized by a universal mobility ${\ensuremath{\mu}}_{0}$ of $30--40\text{ }\text{ }{\mathrm{cm}}^{2}/\mathrm{V}\text{ }\mathrm{s}$. As a result, we can predict the full temperature dependence of their charge transport properties with only the mobility at one temperature known.