Characterization of charge transport and electrical properties in disordered organic semiconductors

Abstract

The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius temperature dependence, cannot well describe the current–voltage (J–V) characteristics of hole-only devices made from disordered organic semiconductors. In this paper, we study the charge transport in a large variety of organic semiconductors and provide evidence for the availability of our improved mobility model based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence. It is validated with experimental data collected from hole-only devices made of different organic materials in a wide range of operating conditions. Furthermore, we calculate and analyze in detail some important electrical properties of the relevant polymers by using a numerical method, adopting the uneven discretization and Newton iteration methods to solve the coupled equations describing the space-charge-limited current. It is shown that the boundary carrier density has a significant effect on the J–V characteristics and that the numerically calculated carrier density is a decreasing function of the distance to the interface.