A 21·5% efficient Cu(In,Ga)Se2 thin-film concentrator solar cell

Abstract

Cu(In,Ga)Se2 (CIGS) solar cells have been designed for operation under 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 CdS window/buffer layer to enhance the short-circuit current at the expense of the open-circuit voltage. Operation of the devices under 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%.