Organic solar cells from water-soluble poly(thiophene)/fullerene heterojunction

We report the characteristics of solar cells with a heterojunction structure con-taining water-soluble polythiophene and a fullerene (C60) (indium tin oxide/sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] (PTEBS:Na+)∕C60∕2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/Al). The devices show that the PTEBS:Na+ layer acts as an electron donor and the photovoltaic effect is dominated by the PTEBS:Na+∕C60 interface. By post-device-fabrication treatment through the application of a positive bias, the devices show a short-circuit current density exceeding 0.97±0.02mA∕cm2, an open-circuit voltage of 0.67±0.02V, a fill factor of 0.53±0.02, and a power conversion efficiency of 0.43±0.02% at AM 1.5 solar illumination (80mW∕cm2).