ZnO/ZnS(O,OH)/Cu(In,Ga)Se/sub 2//Mo solar cell with 18.6% efficiency

We report on recent enhancements to device performance leading to a certified total-area energy conversion efficiency of 18.6% for Cu(In,Ga)Se/sub 2/ solar cells that incorporate a ZnS(O,OH) buffer layer as an alternative to CdS. Along with information on device fabrication and layer properties, we provide a comparative device analysis between this type of solar cell and the slightly more efficient ZnO/CdS/Cu(In,Ga)Se/sub 2//Mo solar cell structure. This comparative study allows us to elucidate the areas for optimization in the quest for conversion efficiency above 20% in thin-film polycrystalline solar cells. It quantifies the gains in current generation due to superior collection at short wavelengths, as well as the somewhat lower voltage and infrared response.