Organic photovoltaics (PV) offer advantages like flexibility, low weight and cost, and environmentally benign materials. Despite power conversion efficiencies reaching around 19%, they lag behind inorganic PVs due to high open-circuit voltage (Voc) losses. This paper presents an electrostatic model of a rough donor-acceptor interface, experimentally tested on small molecule PV materials. The model links Voc, photovoltaic gap, charge-transfer state energy, and interfacial morphology, showing that electrostatic bias reduces the photovoltaic gap. However, this negative effect on Voc can be mitigated by adjusting the donor-acceptor interface morphology.

Carl Poelking, Johannes Benduhn, Donato Spoltore, Martin Schwarze, Steffen Roland, Fortunato Piersimoni, Dieter Neher, Karl Leo, Koen Vandewal, Denis Andrienko