BiFeO3 (BFO) has attracted much research attention as the material has variety of properties, including multiferrioc effect, photovoltaic effect and high specific electrical capacitance. In this work, we have measured the photovoltaic effect and electrical capacitance of Cu-doped BiFeO3 synthesized by the simple solution method. Then we construct a so-called "solar supercapacitor" which can both generate electricity and store energy in one single device. This provides a conceptual guideline which help reducing the cost of components for the solar cell system with energy storage. It also demonstrates a new type of simple device which can measure accumulated solar energy as a function of time. [ABSTRACT FROM AUTHOR]