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Stion to build double-layered thin-film solar

Solar start-up Stion raises $70 million to ramp up its production of thin-film solar modules and to build a panel with two layers of solar cells to improve efficiency.

Stion, one of dozens of companies racing to oust current solar market leaders, has raised $70 million to ramp up production of its thin-film solar cells and modules.

The San Jose, Calif.-based start-up said on Wednesday it has raised $50 million from Taiwanese Semiconductor Manufacturing Company (TSMC), which will take a 21 percent stake in Stion and produce solar panels for it. Existing investors Khosla Ventures, Braemar Energy Ventures, Lightspeed Venture Partners, and General Catalyst Partners also invested, bringing the total Stion has raised since 2006 up to $114.6 million.

Thin-film solar panel from Stion Stion

This latest, series D round will be used to expand its current San Jose facility to produce 100 megawatts' worth of solar panels per year, up from the current pace of 10 megawatts.

The company expects to ship its first products next month and is in the process of lining up installers and distributors who serve the commercial market, said President and CEO Chet Farris. The company uses a combination of copper, indium, gallium, and sulfur-selenide (CIGSS) for its cells.

Stion is one of dozens of companies formed in the past five years to pursue thin-film solar technology, which promises to be cheaper than silicon for cells because of cheaper manufacturing processes. But despite a lot of money invested, many of these companies are still struggling to scale up their operations.

Farris said the company is partnering with TSMC partly to save the capital cost of building production facilities. Rather than design and build its own machines, most of its sputtering manufacturing equipment is off-the-shelf from the glass industry, he said.

"We're really focused on the material science, the process, and the device structure," he said. "People ask us what's the one the unique thing about us, but the reality is that the devil is in the details and it's a whole bunch of little things."

The company's target cost is to be about 80 cents or 85 cents per watt, which would be less than the $1-per-watt cost touted by thin-film solar front-runner First Solar.

So far, the company has managed to get the efficiency of its panels in the range of 10 percent to nearly 12 percent.

Next year, it plans to start manufacturing a "tandem" solar panel that will stack another layer of solar cell on top of a bottom layer. The material for the different layers is tuned to capture different light. The double module will improve efficiency by 35 percent and have the same cost per watt as the single-layer module, Farris said.

Stion plans to manufacture its own modules and license technology to others. That business model, combined with cheaper solar power, will allow it to stick out from the pack, said Farris.

"You have to have a product that's fairly differentiated or you just won't survive. We'll see more of that going forward," he said.