High Stability Near-Broken Gap Junction for Multijunction Photovoltaics

Glenn Teeter, Joel Pankow, Forrest Johnson, Brian Benton, Stephen Campbell

Research output: Contribution to journalArticlepeer-review

3 Scopus Citations


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 languageAmerican English
Article number011201
Number of pages8
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Issue number1
StatePublished - 1 Jan 2019

Bibliographical note

Publisher Copyright:
© 2018 Author(s).

NREL Publication Number

  • NREL/JA-5K00-73192


  • band gap
  • chemical elements
  • contact impedance
  • photovoltaics
  • thin films
  • transition metal oxides
  • visible spectra
  • work functions


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