The origin of collected charge and open-circuit voltage in blended polyfluorene photovoltaic devices

Polymer blend photovoltaic devices (see Figure) are investigated and the characteristic electron and hole lengths estimated. It is found that for a polymer film exhibiting fine-scale phase separation, only charges generated close to the electrode can be collected. The open-circuit voltage for polymer blend devices is found to be lower than that for bilayer devices, a result of the direct paths from cathode to anode within each blend component.