Doping effects for organic photovoltaic cells based on small-molecular-weight semiconductors

We have studied highly efficient organic photovoltaic (OPV) cells based on small-molecular-weight semiconductors: zinc phthalocyanine (ZnPc) and C60. To improve the efficiency furthermore, open-circuit voltage (Voc) has to be increased. We reported that 5,6,11,12-tetraphenylnaphthacene (rubrene) produces the highest Voc of 0.91 V by p–n heterojunction OPV cells with C60. In this paper, we report rubrene doping effects for OPV cells based on ZnPc to obtain higher Voc.