Reactive sputtering of ZnO/ZnO:Al contacts for chalcopyrite solar modules

Reactive sputtering is an option to further reduce costs associated with the deposition of the transparent front contact for chalcopyrite-based solar modules. Our approach here is to develop a proof of concept for a ZnO window, where the i-ZnO and the doped ZnO:Al are both sputtered in a reactive process. It is shown, that on cell level the device performance is preserved when replacing the standard RF processes with the fully reactive process. It is also shown, that the series resistance of module test structures increases with reactively sputtered ZnO. This finding, as well as a reduced damp heat stability of mini modules without encapsulation are tentatively assigned to an increased contact resistance and corrosion at the Molybdenum/ZnO interface within the interconnects.