  By applying Monte Carlo simulations we found that the extraction of bound
polaron pairs (PP) at the electrodes is an important loss factor limiting the
efficiency of organic optoelectronic and photovoltaic devices. Based upon this
finding, we developed a unified analytic model consisting of exact Onsager
theory, describing the dissociation of PP in organic donor-acceptor
heterojunctions, the Sokel-Hughes model for the extraction of free polarons at
the electrodes, as well as of PP diffusion leading to the aforementioned loss
mechanism, which was not considered previously. Our approach allows to describe
the simulation details on a macroscopic scale and to gain fundamental insights,
which is important in view of developing an optimized photovoltaic device
configuration.
