Brownian motion field dependent mobility theory of hopping transport process

Abstract

A Brownian motion theory of hopping mobility has been formulated based on the one-dimensional hopping conduction model between localized states. The probability of hopping in the direction of the applied electric field and the duration of the hop between the localized states are assumed to be field dependent and thermally activated. The general form of the Brownian motion mobility model fitted well with the time of flight results measured in the low field regime and for most part of the mobility data extracted from the space charge limited conduction applied to tris-(8-oxyquinolato) aluminum (Alq3) in higher field regime. The Brownian motion model can be modified in order to account for the dependence of charge mobility in the higher electric field regime and at higher temperatures. The variation of charge mobility with applied electric field was fitted using the Brownian motion theory. The hopping time and the hopping distance were extracted from the fit and found to be about 3ps and 0.9nm, respectively for Alq3 at room temperature.