Enhancement in open circuit voltage through a cascade-type energy band structure

In this paper, we report a method to increase the open-circuit voltage (VOC) of an organic solar cell by inserting an interfacial layer between the donor and acceptor layers to form a cascade-type energy band structure. We demonstrate its feasibility using a recently reported asymmetric pentacene derivative, tetraceno[2,3-b]thiophene (TT) as a donor material, C60 as an acceptor material, and copper phthalocyanine (CuPc) as the sandwich layer. The VOC was increased from 0.3V for the device with no CuPc sandwich layer to 0.56V for 13nm thick CuPc layer. The power conversion efficiency (PCE) of the device with 13nm CuPc layer was 1.53% and the fill factor (FF) was 0.64, in comparison to TT∕C60 device which had a PCE of 0.78% and a FF of 0.52.