Abstract
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 | American English |
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Article number | 011201 |
Number of pages | 8 |
Journal | Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films |
Volume | 37 |
Issue number | 1 |
DOIs | |
State | Published - 1 Jan 2019 |
Bibliographical note
Publisher Copyright:© 2018 Author(s).
NREL Publication Number
- NREL/JA-5K00-73192
Keywords
- band gap
- chemical elements
- contact impedance
- photovoltaics
- thin films
- transition metal oxides
- visible spectra
- work functions