A system comprising a plurality of organic photovoltaic cells arranged in a stack disposed between a first electrode and a second electrode, and a resistive load electrically connected across the first electrode and the second electrode. Each cell comprises a rectifying junction at an interface of organic semiconductor materials. There is metal or metal substitute disposed in the stack between each of the cells. At least a first cell and a second cell of the plurality of organic photovoltaic cells have different absorption characteristics. Photocurrent from the plurality of organic photovoltaic cells energizes the resistive load.