Novel Contacts of Solar Cells and Other Optoelectronic Devices


Thin-film cadmium telluride (CdTe) solar cells are the second most common photovoltaic technology after crystalline silicon, and make up approximately 5% of the global market. CdTe solar cells occupy 40% of the United States photovoltaic market, and offer competitive advantages over imported silicon products on cost, production time, and energy yield. However, silicon solar cells hold a higher power conversion efficiency at 26.7%, compared to the current 22% record efficiency for CdTe cells.

There are a few challenges to overcome in order for CdTe cells to achieve higher power conversion efficiency. First, there is a lack of materials with large work-function or low valence band edge for hole-selective contact to CdTe. There is also a lack of non-destructive measurements of material properties including band offset and its correlation to actual device performance. This results in a lack of meaningful feedback provided to improve device design and manufacturing processes.

Invention Description

Researchers at Arizona State University have developed a novel set of materials in combination with surface or interface states to form a “pinned” Fermi level substantially above the valence band edge for n-type or p-type contact for optoelectronic devices. This invention uses the surface Fermi level pinning effect to build an electrical field inside of a semiconductor to extract or inject carriers for solar cells, photodetectors, and light-emitting device applications. Indium tin oxide (ITO) can be put on top of the novel two-dimensional materials to form multilayer practical contacts.

Potential Applications

  • Thin film solar cells
  • Infrared (IR) detectors
  • Radiation detectors
  • Light-emitting devices

Benefits & Advantages

  • Non-metallic contacts can be transparent
  • Can enable bifacial thin film solar cells, including CdTe solar cells
  • Improved efficiency over current CdTe solar cells (>23%)

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