Copper indium gallium selenide

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Copper indium gallium selenide (CIGS) is a new semiconductor material comprising copper, indium, gallium, and selenium. The material is a solid solution of copper indium selenide (often abbreviated "CIS") and copper gallium selenide, with a chemical formula of CuInxGa(1-x)Se2, where the value of x can vary from 1 (pure copper indium selenide) to 0 (pure copper gallium selenide). It is a tetrahedrally-bonded semiconductor, with the chalcopyrite crystal structure, and a bandgap varying continuously with x from about 1.0eV (for copper indium selenide) to about 1.7eV (for copper gallium selenide)

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[edit] Use and Manufacture

Its main use is for photovoltaic cells ([[CIS solar cells|CIGS cells]]), in the form of polycrystalline thin films. Unlike the silicon cells based on p-n junction, the structure of CIGS is a complex heterojunction system. The best efficiency achieved as of December 2005 was 19.5% reported by Contreras et al [1]. Just recently the team at the National Renewable Energy Laboratory achieved 19.9% new world record efficiency by modifying the CIGS surface and making it look like CIS[2]. . This idea was first introduced by Dr. Jehad AbuShama in the IEEE conference in 2005[3]. The 19.9% efficiency is by far the highest compared with those achieved by other thin film technologies such as Cadmium Telluride (CdTe) or amorphous silicon (a-Si). [4]

As for CIS, and CGS solar cells, Dr. Jehad AbuShama reported the world record total area efficiencies of 15.0% and 10.2% respectively. [5]

CIGS films can be manufactured by several different methods. The most common vacuum-based process co-evaporates or co-sputters copper, gallium, and indium, then anneals the resulting film with a selenide vapor to form the final CIGS structure. A non-vacuum-based alternative process deposits nanoparticles of the precursor materials on the substrate and then sinters them in situ.

CIGS solar cells are not as efficient as crystalline silicon solar cells -- they are only about half as efficient, but they are expected to be substantially cheaper. CIGS can be printed directly onto molybdenum coated glass sheets. Solar cells made from crystalline silicon are made of slices of solid silicon and require therefore more expensive semiconductor material.

[edit] History

The market segment leader is Global Solar, which is already selling flexible, portable solar chargers.[6] Venture capitalists have poured more than $344 million into five CIGS companies in the last few years--Nanosolar, Miasolé, Solopower, Solyndra, and Heliovolt.[7]

[edit] See also

[edit] References

  1. ^ Miguel Contreras, Kannan Ramanathan, Jehad AbuShama, Falah Hasoon, David Young, Brain Egaas and Rommel Noufi “Diode Characteristics of State-of-the art ZnO/CdS/Cu(In1-xGax)Se2 Solar Cells,” Progress in Photovoltaics: Research and Applications 13, 209 (2005 )
  2. ^ Ingrid Repins, Miguel A. Contreras, Brian Egaas, Clay DeHart, John Scharf, Craig L. Perkins, Bobby To, Rommel Noufi,19.9%-efficient ZnO/CdS/CuInGaSe2 solar cell with 81.2% fill factor, Progress in Photovoltaics: Research and Applications 16, 235 (2008)
  3. ^ Jehad A. AbuShama, R. Noufi, S. Johnston, S. Ward, and X. Wu, “Improved Performance in CuInSe2 and Surface-Modified CuGaSe2 (CGS) Thin Film Solar Cells,” Proceedings of 31st IEEE Photovoltaic Specialists Conference, Lake Buena Vista, Florida, January 2005.
  4. ^ Noufi, Rommel; Ken Zweibel. HIGH-EFFICIENCY CDTE AND CIGS THIN-FILM SOLAR CELLS: HIGHLIGHTS AND CHALLENGES. National Renewable Energy Laboratory.
  5. ^ Jehad A. AbuShama, R. Noufi, S. Johnston, S. Ward, and X. Wu, “Improved Performance in CuInSe2 and Surface-Modified CuGaSe2 (CGS) Thin Film Solar Cells,” Proceedings of 31st IEEE Photovoltaic Specialists Conference, Lake Buena Vista, Florida, January 2005.
  6. ^ Forecast: Sunny for small tech in solar
  7. ^ HelioVolt raises more cash

[edit] External links