a solar cell . the solar cell includes a substrate , a first layer comprising a first copper - based material deposited upon the substrate , the first copper - based material electrically attracted to the substrate or to a first optional deposit layer deposited between the substrate and the first layer , and a second layer comprising a second copper - based material deposited upon the first layer or an second optional deposit layer deposited between the first layer and the second layer , the second copper - based material electrically attracted to the first layer or to the second optional deposit layer , wherein the first copper - based material and the second copper - based material are selected from the group consisting of copper indium gallium selenide , copper indium selenium , and cadmium sulfate .