On a roll

Toledo, Ohio-based Xunlight Corporation has demonstrated that it can produce thin-film silicon PV modules using its roll-to-roll manufacturing process.

Toledo, Ohio-based Xunlight Corporation has demonstrated that it can produce thin-film silicon PV modules using its roll-to-roll manufacturing process.

The process allows the company to make triple-junction thin-film silicon solar cells on rolls of thin stainless-steel substrates, 3ft wide and up to one-mile long.

The long stainless-steel web is guided through a series of vacuum chambers for the deposition of nine semiconductor layers using a plasma-enhanced chemical vapour deposition process and back reflector and top electrode layers using a sputtering process.

The combined thickness of the layers for the triple-junction solar cell is approximately one hundredth of the thickness of a typical sheet of paper.

Xunlight designed, developed, engineered and built its own manufacturing equipment with the assistance of its academic partner, the University of Toledo’s Thin Film Silicon Photovoltaic Laboratory.

Using its 3ft-wide roll-to-roll manufacturing line, Xunlight has produced large-area (3ft by 5ft and 3ft by 18ft) flexible PV modules. The 3ft by 5ft modules, measured with a Spire Solar Simulator (Spi-Sun Simulator 4600SLP), demonstrated 8.77 per cent initial aperture-area efficiency, which, after extended light exposure, is expected to stabilise at 7.4 per cent aperture-area module efficiency.

Xunlight has received more than $40m (£25m) of institutional investments from Emerald Technology Ventures, Trident Capital, NGP Energy Technology Partners and Rabo Ventures.

The company has also received more than $13m of funding from the US Department of Energy, US Department of Commerce and Ohio Department of Development (ODOD), and a $7m loan from the State of Ohio to develop its products and manufacturing process.