Copper oxide-modified graphene anode and its application in organic photovoltaic cells

Graphene is an ideal substitute for indium tin oxide electrode in organic photovoltaic (OPV) devices, due to its outstanding electrical, optical, chemical and mechanical properties. However, the graphene electrode suffers from work function mismatch with common hole injection layer and intrinsic hydrophobic property. Here, Cu_xO is proposed to modify monolayer graphene in order to increase the work function of graphene (from 4.45 to 4.76 eV) and decrease the water contact angle (from 88° to 59°). Then, the OPV devices based on the Cu_xO modified graphene anode are fabricated successfully, and power conversion efficiency (PCE) is enhanced from 4.00 ± 0.44 to 5.23 ± 0.47%. Furthermore, the ternary blended polymer solar cell is fabricated by adding a small molecular material 1, 2, 5-thiadiazole-fused 12-ring polyaromatic hydrocarbon into the active layer, and the PCE is improved to 6.03 ± 0.53%, due to the enhanced absorption and depressed recombination inside the active layer.