Ionic Space-Charge Effects in Solid State Organic Photovoltaics

The effect of mobile ions on the operation of donor-acceptor bilayer solar cells is studied. We demonstrate the large. effect ions can have on the energetics of the solar cells, illustrated by (for Instance) changing the output voltage of a cell In situ from 0.35 to 0.74 V. More importantly, ills shown ionic species do not obstruct the charge generating properties of the photovoltaic devices and ionic space charge can be used in situ to improve their efficiencies. The results obtained are explained by taking into account energetic changes at the donor-acceptor interface as well as built-in potentials, giving clear guidelines on how Ionic species can offer many new and exciting functionalities to organic photovoltaics.