Energy disorder reduces the achievable open-circuit voltage in organic bulk-heterojunction solar cells. Here the effect of disorder on charge carrier recombination flux is numerically modeled. The recombination current follows an exponential dependence on voltage (Fermi level splitting) parameterized by beta (inverse of the diode ideality factor), which reduces the power conversion efficiency through lower fill factors. beta-Parameter approaches unity (Boltzmann approximation) at room temperature only in the case of weak disorder (sigma approximate to 50 meV). For larger disorder values (sigma >= 100 meV) usually encountered in real devices, a huge reduction in beta (open-circuit voltage, and fill factor) is predicted following a relationship as beta proportional to ln sigma(-1). (C) 2012 Elsevier Ltd. All rights reserved.