Amorphous organic molecule/polymer diodes and transistors—Comparison between predictions based on Gaussian or exponential density of states

Abstract

We examine the role of the density of states in determining the performance of amorphous organic devices. Specifically we compare the exponential density of states and the Gaussian density of states. We find that the shape of the density of states affects dramatically the ideality factor of P–N diodes and the gate voltage dependence of the mobility in field effect transistors. By comparing to experimental results we conclude that a real DOS should have the attributes found in Gaussian density of states. Also, since the Gaussian density of states do not easily allow to produce simple analytical expressions, methods that are developed for Gaussian density of states can more easily be adapted to real shapes of density of states which are not necessarily described by a single Gaussian.