Electron transport in polyfluorene-based sandwich-type devices: Quantitative analysis of the effects of disorder and electron traps

Results of a combined experimental and modeling study of electron transport in a blue-emitting polyfluorene-based copolymer in sandwich-type devices are presented. We show how, for wide temperature and layer thickness ranges, an accurate and internally consistent drift-diffusion model description of the voltage-dependent current density can be obtained. We employ an adapted form of the "extended Gaussian disorder model," within which the density of states (DOS) is described as a superposition of a Gaussian DOS and an exponential DOS ("trap states"), characterized by only a small set of physically meaningful parameters. A comparison is made with the hole mobility reported for related polymers.