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 (C-60) (indium tin oxide/sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] (PTEBS:Na+)/C-60/2,9-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+/C-60 interface. By post-device-fabrication treatment through the application of a positive bias, the devices show a short-circuit current density exceeding 0.97 +/- 0.02 mA/cm(2), an open-circuit voltage of 0.67 +/- 0.02 V, a fill factor of 0.53 +/- 0.02, and a power conversion efficiency of 0.43 +/- 0.02% at AM 1.5 solar illumination (80 mW/cm(2)). (c) 2007 American Institute of Physics.