Charge transport in organic materials with quasi-Gaussian density of states

Abstract

Opto-electronic devices based on organic semiconductors have garnered significant research interest in recent years, with transport energy being a critical factor governing their performance. The density of states (DOS) plays a key role in modulating transport energy within these materials, thereby influencing charge carrier mobility and the Einstein relation. In this work, the carrier transport within a set of quasi-Gaussian DOSs, g(E)∝exp[−(E/σ)p] with 1 ≤ p ≤ 2, is examined. We systematically investigate the effects of DOS distribution width, power p, carrier concentration, and material parameter Nα3 on transport energy. It is observed that at high carrier concentrations, the transport energy exhibits a pronounced dependence on concentration variations. Furthermore, the generalized Einstein relation (GER) and the behavior of mobility are studied by adjusting the lower integration limit of the carrier concentration in GER expression to Et. Our findings only deviate slightly from the classical Einstein relation. Subsequently, the experimental data of a small-molecule material and a polymer material are fitted, and the power p is determined by using the approach established by Oelerich et al. The resulting trend in mobility demonstrates approximately agreement with experimental data. These results offer additional alternatives for this field and provide valuable insights for reference.