An improved unified description of the dependence of the charge-carrier mobility on temperature, carrier density, and electric field in disordered organic semiconductors is proposed based on the Arrhenius temperature dependence ln(mu) proportional to 1/T and non-Arrhenius temperature dependence ln(mu) proportional to 1/T(2). The improved description of the mobility can quite well fit the numerical solution of the master equation at both the low densities and high densities, the latter of which cannot be accurately described using the model introduced by Pasveer et al. [6]. Experimental current-voltage characteristics in devices based on organic semiconductors are also excellently reproduced with this improved description. Finally, we calculate and analyze the distribution of the charge-carrier density and electric field with position in polymer layer for two organic semiconductors in detail by using the improved description. (C) 2010 Elsevier B.V. All rights reserved.