Copper indium gallium selenide
Copper indium gallium selenide (CIGS) is a new semiconductor material composed of 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)
Use and Manufacture
Its main use is for photovoltaic cells (CIGS cells), in the form of polycrystalline thin films. Unlike the silicon cells based on a homojunction p-n junction, the structure of CIGS is a more 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, for which the record efficiency lies at 24.7%[6], 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.
History
The market segment leader is Global Solar, which is already selling flexible, portable solar chargers.[7] Venture capitalists have poured more than $344 million into five CIGS companies in the last few years--Nanosolar, Miasolé, Solopower, Solyndra, and Heliovolt.[8]
See also
References
- ^ 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 )
- ^ 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)
- ^ 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.
- ^ Noufi, Rommel. "HIGH-EFFICIENCY CDTE AND CIGS THIN-FILM SOLAR CELLS: HIGHLIGHTS AND CHALLENGES". National Renewable Energy Laboratory.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ 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.
- ^ M.A. Green, Jianhua Zhao, A. Wang and S.R.Wenham, "Very high efficiency silicon solar cells-science and technology", IEEE Transactions on Electron Devices 46(10), 1940, October 1999
- ^ Forecast: Sunny for small tech in solar
- ^ HelioVolt raises more cash
External links
- Copper Indium Diselenide Publications, Presentations, and News Database of the National Renewable Energy Laboratory.
- Michael Kanellos Silicon vs. CIGS: With solar energy, the issue is material October 2, 2006 CNET News.com
- National Pollutant Inventory - Copper and compounds fact sheet