Optical analysis of II–VI alloys and structures for tandem PV

This study focuses on the development of an optical property database through spectroscopic ellipsometry analysis of II–VI polycrystalline alloy thin films for tandem photovoltaics. The materials of interest for the active layer components in this application include top cell Cd1-xMgxTe and bottom cell HgxCd1-xTe. Such materials are being explored for use in current-matching two-terminal -- as well as four-terminal -- device configurations. With complete optical properties tabulated for the alloys and for the other device components, including transparent back contacts of doped ZnTe for the top cells and transparent interconnect junctions of In2O3:Sn between cells, tandem designs can be developed that not only optimize thicknesses of the components but also minimize optical losses to ensure highest performance. Initial quantum efficiency simulations have been performed in this study that exemplify this strategy.