Does the Temperature Dependence of the Charge Carrier Mobility in Disordered Organic Semiconductors at Large Carrier Concentrations Obey the Meyer-Neldel Compensation Law?

The temperature-activated charge transport in disordered organic semiconductors at large carrier concentrations has been thoroughly considered, by using a recent analytical model [Phys.Rev.B 76, 045210 (2007)] assuming a Gaussian density-of-states (DOS) distribution and Miller-Abrahams jump rates. We demonstrate that the apparent Meyer-Neldel compensation rule is recovered with regard for the temperature dependences of the charge carrier mobility upon varying the carrier concentration, but not for varying the DOS distribution width. We show that this phenomenon is entirely due to the evolution of the occupational DOS distribution as a function of the state filling. Predictions of the model are in a quantitative agreement with available experimental results.