Nikkei Electronics Asia -- November 2009
Green Device -- Report
CIGS Solar Cells Lead in Performance, Cost

At last a leader has emerged from the pack in next-generation solar cell technologies: copper indium gallium selenide (CIGS) solar cells. The technology utilizes a compound semiconductor made from copper, indium, gallium, selenium and sulfur as the active layer. The active layer is thin (no more than 2um), making them a type of thinfilm solar cell. The technology has already been used in satellites where improved resistance to ultraviolet radiation and other characteristics have proved highly valuable.

The major bottleneck with the technology has been difficulty in volume production, but an increasing number of firms have accumulated sufficient manufacturing know-how to budget for major production expansions. According to survey firm Displaybank Co Ltd of Korea, production capacity was 103MW in 2007 and 313MW in 2008, but is expected to surge to 3645MW in 2013, accounting for about 20% of total solar cell production.

High Efficiency, Low Cost

Of these manufacturers (see Fig), one of the most aggressive is Showa Shell Solar Co Ltd of Japan, a subsidiary of Showa Shell Sekiyu KK of Japan. The firm's No.2 Plant began full-scale operation in Jun 2009, boosting total solar cell panel capacity together with the No.1 Plant to 80MW/year. The firm has also budgeted Yen100 billion to construct a No.3 Plant with an annual production capacity of 900MW, slated to begin volume production in 2011.

The firm plans to continue investment through 2012, and according to a company source will build fourth and fifth plants in "high-demand nations and regions". They hope to command 10% of global solar cell production volume by 2014, which would be 2GW/year to 3GW/year.

In addition to being one of the most productive firms in the business, Showa Shell Solar is also a frontrunner when it comes to CIGS solar cell energy conversion efficiency, low cost and other characteristics. There are reports in the literature of CIGS solar cells achieving efficiencies of 19.9%, but efficiency is still generally under 12% for volume-production cells. In the spring of 2009, however, the company achieved 15.7% conversion efficiency in a 30cm-square module, very close to volume-production specifications. As a result, amorphous Si solar cells, with efficiencies of about 10%, aren't competitive any longer.

The company is stressing low cost most of all, but commented: "The decision to build the No.3 Plant was based on recognition of our competition with First Solar Inc of the US."

The firm expects to be able to generate electricity for no more than Yen100/W, which is no more than 70% of the manufacturing cost of most poly-Si solar cells. First Solar's cells are cadmium-tellurium (CdTe) type; it is unclear due to environmental concerns whether they will gain widespread adoption.

The only possible worry is with assuring a stable supply of indium, a rare metal, but Kameda expresses confidence: "CIGS solar cells use only a minute amount of indium. Japanese domestic recycling is making good progress, and imports from China are down to a small trickle. I have no worries about assuring supply for the next five years."

Overseas Challengers

As far as production scale, performance and a few other points go, most of the competitors following in Showa Shell Solar's footsteps are based outside Japan, and use unique technologies. Solyndra Inc of the US, for example, uses florescent lamp glass tubes as the substrate. Nanosolar Inc of the US and at least three others manufacture very low-cost, flexible solar cells roll-to-roll. Solyndra has received massive support, including funding of over Yen50 billion from the US government. 

If these manufacturers get their operations up and running smoothly, they will be producing several GW/year each, making it likely that production volume will leap past that of poly-Si solar cells.

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