Realization of efficient semitransparent organic photovoltaic cells with metallic top electrodes: utilizing the tunable absorption asymmetry

Abstract

Efficient semitransparent organic photovoltaic (OPV) cells are presented in an inverted geometry employing ZnS/ Ag/ WO(3) (ZAW) as a top anode and ITO/ Cs(2)CO(3) as a bottom cathode. Upon identification of the light absorption that differs depending on the illumination direction, the degree of the absorption asymmetry is tuned by varying the ZAW structure to maximize the efficiency for one direction or to balance it for both directions. Power conversion efficiency close to that of conventional opaque OPV cells is demonstrated in semitransparent cells for the ITO side illumination by taking advantage of the internal reflection occurring at the organic/ZAW interface. Cells with efficiencies that are reduced but balanced for both illumination directions are also demonstrated. (C) 2010 Optical Society of America