High stability near-broken gap junction for multijunction photovoltaics
- Univ. of Minnesota, Minneapolis, MN (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
High performance tunnel junctions were made from sputtered and annealed p-type CuAlO2 and n-type ZnSnO3 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 degrees C. This is a key requirement for many high performance multijunction thin film inorganic solar cells. The CuAlO2 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 degrees C and above, Cu is in the +1 oxidation state. This suggests that annealing is necessary to form CuAlO2. A near-broken gap alignment provides a low resistance contact with band alignment that is nearly ideal for a tandem device.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- Grant/Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1492937
- Report Number(s):
- NREL/JA-5K00-73192
- Journal Information:
- Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Vol. 37, Issue 1; ISSN 0734-2101
- Publisher:
- American Vacuum SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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