Improvement of Characteristics of Organic Photovoltaic Devices Composed of Conducting Polymer-Fullerene Systems by Introduction of ZnO Layer

Photovoltaic cells, which consist of a heterojunction of conducting polymer-fullerene systems and a zinc oxide (ZnO) thin film, have been studied. In this structure, an incident photon is used effectively because exciton generation and dissociation, which contribute to photocurrent, mainly occur on the light incident side in a conducting polymer layer. In the layered photovoltaic cells with the structure of indium-tin-oxide (ITO) / ZnO / fullerene / conducting polymer / Au, a monochromatic energy conversion efficiency of 5.2% under 0.6 mW/cm2 illumination at 500 nm and an external quantum efficiency reaching 74% at the peak wavelength have been realized, which can be explained by the interpenetrated fullerene / conducting polymer interface and the short distance between the electron-generation region and electrode enhancing electron collection to the electrode.