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CIGS-based solar cells achieve efficiency breakthrough

Posted: 30 Jan 2008 ?? ?Print Version ?Bookmark and Share

Keywords:solar cells? copper indium gallium diselenide (CIGS)? thin-film technology?

Global Solar Energy Inc. has claimed a breakthrough for solar cells based on copper indium gallium diselenide (CIGS) thin-film technology. GSE said that its CIGS-based thin-film cells have achieved an average of 10 percent efficiency "on a flexible, lightweight substrate over several production runs." Starting in 2007, the company's solar cells achieved an average efficiency of about 9 percent.

The privately-held company is also expanding its production base amid the ongoing growth in the solar-cell industry. It plans to announce a new plant in the U.S. state of Arizona, which is slated for production in March. Last year, GSE announced a new plant in Berlin, Germany, which is scheduled for production in mid-2008.

Growing market
In 2007, GSE capped off a record year in which the company manufactured and shipped 4MW of photovoltaic products. Over time, the company hopes to have a total capacity of 65MW.

Other thin-film, solar-cell suppliers, including First Solar Inc. and United Solar Ovonic, are also in the process of expanding their capacities. "The demand for solar energy is still pent up," said Tim Teich, VP of sales and marketing at GSE, in an interview.

Thin-film products are especially hot, given the ongoing shortages of polysilicon materials. Conventional solar cells make use of polysilicon, while the thin-film products use little or none of these materials.

"We are still in that mode," said Jeffrey Britt, VP of technology at GSE. "There is still a polysilicon shortage. Demand still exceeds supply."

Despite the excitement for thin-film products, the market is becoming overcrowded with a slew of startups with unproven technologies. In the CIGS segment alone, DayStar, HelioVolt, Iset, Miasole, Nanosolar, Solyndra and others have emerged.

GSE claims to be ahead of its new rivals, many of which have been unable to get their products out the door. Founded in 1996, GSE began to produce its first CIGS-based solar cells in 2004.

While other companies produce CIGS on glass, GSE claims to be the only company with CIGS on flexible materials. GSE uses a "roll-to-roll" and a vacuum deposition manufacturing process, enabling lightweight, flexible cells.

The company's proprietary process claims to produce among the "highest efficiency" solar cells in the thin-film market. In comparison, high-flying First Solar, which uses a cadmium telluride (CdTe) technology, is said to have efficiencies in the 10 percent range. First Solar's average module conversion efficiency is 10.5 percent as of September 2007, according to that company.

Conventional cells have higher efficiencies, but these products are becoming more expensive due to the soaring costs of polysilicon materials. SunPower Corp. has demonstrated a cell at efficiencies of over 20 percent.

GSE has made a big step by boosting its average efficiency to 10 percent. "This is a big milestone," Britt said. "A number of CIGS thin-film companies have exceeded 10 percent efficiency in the lab or in individual cells, but achieving 10 percent average solar cell efficiency over the course of several sustained, continuous production runs is a significant achievement."

Still, the biggest issue in solar is cost. "Solar electricity prices are today, around 30 cents per kWh, which is two to five times average residential electricity tariffs," according to SolarBuzz, a consulting firm.

But prices continue to drop for the technology. "The prices for high power band solar modules has dropped from around $27 per Wp in 1982 to around $4 per Wp today," according to the firm.

"As of January 2008, there are currently 185 solar module prices below $4.75 per watt, or 11.7 percent of the total sample. This compares with 215 prices below $4.75 per watt in December," according to the firm.

"The lowest retail price for a multicrystalline solar module is $4.28 per watt from a U.S. retailer. The lowest retail price for a monocrystalline module is $4.35 per watt, also from a U.S. retailer," it said. "The lowest thin-film module price is at $3.66 per watt from a European retailer. As a general rule, it is typical to expect thin-film modules to be at a price discount to crystalline silicon."

- Mark LaPedus
EE Times

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