CIGS is a compound of copper, indium, gallium and selenium (Cu(In,Ga)Se2). When combined in the proper ratios, these materials form a semiconductor that can be applied as a thin film to create photovoltaic cells on many carrier substrates. The CIGS ("absorber") layer absorbs photons, the first step in the transformation of solar energy to electricity.
Advantages over Crystalline Silicon
CIGS solar cells offer several advantages over crystalline silicon solar cells. In particular, CIGS cells are:
# Less expensive per Watt
# More efficient in low-angle and low-light conditions
# Extremely lightweight
# Flexible enough to conform to small-radius curves
# Stable and reliable (even self-healing) in real-world conditions
These advantages are further enhanced when incorporated with flexible encapsulants into flexible photovoltaic modules that Miasolé now manufactures in high volume.
Under the Hood
CIGS is a direct band-gap semiconductor (in contrast to crystalline silicon, which is an indirect band-gap semiconductor). This difference is crucial, as it allows CIGS films to generate far more electricity per unit of material. A CIGS film as thin as 1 micron produces a photoelectric effect equal to that of a crystalline silicon wafer 200-300 microns thick. In other words, CIGS cells use less than 1% of the semiconductor material required by crystalline silicon cells, which yields an inherent (and sustainable) cost advantage.
The CIGS photovoltaic effect was first discovered in the 1970s. Since then, government and university labs have dramatically advanced the understanding and efficiency of CIGS material, achieving 19.5% conversion efficiency at the Department of Energy's National Renewable Energy Lab (NREL). This level of efficiency is comparable to polycrystalline silicon solar cells, which represent the preponderance of the current production and installed modules in the solar industry. CIGS has also proven to be stable in a field environment, with modules under test for more than fifteen years.
CIGS has been produced commercially in modest volumes for nearly a decade, but the industry has lacked a high-volume manufacturing technology to fully realize its potential. Miasolé differentiates itself by bringing high-volume, thin-film manufacturing technology to the CIGS solar industry. In a broad sense, Miasolé is simply depositing a new set of thin films using technology its team has proven in the hard disk industry. Rather than applying magnetic films, Miasolé is using the same technology to deposit CIGS semiconductor films on a large scale.
Miasolé is excited about the opportunity to combine the solid research work done in the nation's laboratories with Miasolé's high volume thin-film manufacturing expertise. The net result is industrial-scale, low-cost, reliable and US-made solar products that put the power of the sun to work.
HelioVolt selects Texas for its first CIGS plant
Posted by Michael Kanellos
HelioVolt, which plans on producing thin film solar panels made from copper indium gallium and selenide (CIGS), will build a 20-megawatt factory in Austin, Texas, that will start popping out panels in 2008.
The factory will employ about 150 people. The company then hopes to move into mass manufacturing by the first quarter of 2009 as well as expand production capacity.
CIGS solar panels aren't as efficient at converting sunlight into electricity as silicon solar panels, but advocates say that they cost far less to produce. CIGS solar panels can also be placed on glass or polymer sheets. Ideally, a plastic sheet coated with CIGS solar cells could cover the roof of a giant retail outlet and provide the building with a huge percentage of its electricity.
Getting CIGS into mass production, however, has taken some work. HelioVolt, Miasole, and DayStar Technologies have all experienced delays. NanoSolar, in Silicon Valley, just began producing solar cells out of its new factory.
Although each of the CIGS companies will make the same basic product, they each employ a different manufacturing process. He who comes up with a cheap, reliable way to produce finicky CIGS solar cells will be the winner, say analysts. First Solar, which makes cadmium telluride thin film solar cells, can attribute a lot of its success to its manufacturing process, which it has honed for the last few decades.
Earlier this year, HelioVolt raised $101 million. Investors include New Enterprise Associates and the Masdar Clean Tech Fund, an investment group formed by the government of Abu Dhabi.
Venture capitalists have poured more than $344 million into five CIGS companies in the last few years--Nanosolar, Miasole, Solopower, Solyndra, and HelioVolt.