A 21.5% efficient Cu(In,Ga)Se-2 thin-film concentrator solar cell

Cu(In, Ga)Se-2 (CIGS) solar cells have been designed for operation tinder mildly concentrated sunlight. The absorber was deposited via a three-stage evaporation process that has consistently yielded high-performance one-sun devices. The device structure reported here was modified by reducing the thickness of the US window/buffer layer to enhance the short-circuit current at the expense of the open-circuit voltage. Operation of the devices tinder optical enhancement leads to significant increases in the voltage and fill factor. At 14 suns, the open-circuit voltage for this device was 736 mV, the fill factor was 80.5%, and the efficiency was 21.5%. This result represents the first report of a polycrystalline thin-film solar cell with an efficiency in excess of 20%.