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High performance tunnel junctions were made from sputtered and annealed p-type CuAlO 2 and n-type ZnSnO 3 with suitable band alignment for both low resistance and alignment to typical inorganic materials needed for a tandem solar cell. The devices not only exhibit low resistance, they are also thermally stable, capable of sustaining postdeposition temperatures up to 600 °C. This is a key requirement for many high performance multijunction thin film inorganic solar cells. The CuAlO 2 top-layer remains amorphous, providing a diffusion barrier for top cell stack processing. The materials' stack gives a negligible voltage drop, and the visible-spectrum transparency is near 100%. XPS measurements show that unannealed Cu in the Cu-Al-O films is in the +2 oxidation state, while in the films annealed at 500 °C and above, Cu is in the +1 oxidation state. This suggests that annealing is necessary to form CuAlO 2 . A near-broken gap alignment provides a low resistance contact with band alignment that is nearly ideal for a tandem device.
|Original language||English (US)|
|Journal||Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films|
|State||Published - Jan 1 2019|
Bibliographical noteFunding Information:
The authors acknowledge funding from the Department of Energy SunShot grant (No. DEEE0005319). Part of this work was authored in part by Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. DOE Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation (NSF) through the National Nano Coordinated Infrastructure Network (NNCI) under Award No. ECCS-1542202. Part of this work was carried out in the University of Minnesota Characterization Facility, a member of the NSF-funded Materials Research Facilities Network via the MRSEC program. B.B. received support from the University of Minnesota MRSEC under Award No. DMR-1420013 from NSF.
How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 5