independent offset of the photocurrent, which is crucial for high J$_{SC}$ , which depends both on thermal annealing conditions and cathode material. We also propose a possible origin of this offset with the band-bending close to the contacts. Active layer thickness has an influence on this offset, but surprisingly little impact on the shape of J$_{Ph}$ . 6 A model including polaron pair dissociation, based on Braun–Onsager theory, and extraction, based on the work by Sokel & Hughes, can describe our data for different solar cells with a narrow range of parameters. The electric field in the bulk of the cell is greatly reduced by the injection barriers. At zero electric field, polaron pair dissociation efficiency is 40–60 %. Since the maximum power point is close to V$_{POS}$ , where the effective voltage is zero, the photocurrent under operating conditions is largely determined by the voltage independent offset. For best device performance it is necessary to maxi- mize this constant contribution from the contact regions and simultaneously enhance polaron pair dissociation and polaron extraction in the bulk. Using this parameter set, the dissociation efficiency of po- laron pairs in the bulk can be calculated to be 40–60 % at zero field. However, extraction is the limiting factor at low effective voltages. Only at higher effective voltages, the field dependence of polaron pair dissociation determines the shape of the photocurrent. The saturated, voltage-dependent part of the photocurrent J$_{Ph,max}$ is typically 5–8 mA cm − $^{2}$, with higher values for thicker cells. The dielectric constant e$_{r}$ was set to 3.5 and temperature T to 310 K (slightly above room temperature to account for heating under illumination). The µ$_{t}$$_{f}$ product of spatially averaged mobility µ and PP lifetime (with respect to the ground state) $_{t$_{f}$}$= 1 / k$_{f}$ was set to 1–3 · 10 − $^{14}$m2 V − 1 and the PP radius r$_{PP}$ to 1.8–2.0 nm. consequence of the voltage drops at the contacts (Figure 2). Low injection barriers result in a high band bending in vicin- ity of the electrodes and reduced electric field in the bulk of the cell, corresponding to a seemingly greater d . The approx- imation E = V$_{eff}$ / d is therefore flawed. By use of a pulsed measurement technique, we find a point of symmetry for the photocurrent at 0.52–0.64 V in P3HT:PCBM organic solar cells, which agrees with re- sults from capacitance–voltage measurements. Based on our macroscopic simulation, we identify this voltage as the point of flat bands in the bulk of the solar cell, the quasi flat band case, well below the built-in potential. 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