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Ulvac Rolls PECVD for Tandem PV Cells

July 5th, 2009 by kalyan89 in PV-General, R&D reports, SC Company Reports

by Staff, Semiconductor International, June 25, 2009

Ulvac Inc. (Chigasaki, Japan) has developed a plasma-enhanced chemical vapor deposition (PECVD) system for microcrystalline silicon (μc-Si) deposition, aimed at tandem thin-film silicon photovoltaics. Ulvac, which sells turnkey lines for PV manufacturing, said the new system goes on sale next week and will be part of a turnkey line for tandem μc-Si solar cell production. 

Ulvac said amorphous silicon (a-Si) cells have received R&D attention because they use much less silicon than crystalline silicon photovoltaic cells, but with a lower photoelectric conversion efficiency. Tandem PV cells with a μc-Si layer added to an a-Si thin-film solar cell have a higher conversion efficiency, but the manufacturing equipment has been lacking until now, according to Ulvac. Tandem junction cells created by the CIM-1400 system have a 9% improvement in conversion efficiency and a 10% reduction of the manufacturing cost per watt over a-Si PV, Ulvac said.

“To produce high-performance thin-film silicon photovoltaic modules, the silicon thin films need to be formed at a low deposition rate. In addition, to form μc-Si thin films with high conversion efficiency, a thicker film is required compared to the a-Si thin film,” Ulvac said. The company said the CIM-1400 “for the first time, allows productive high-efficiency μc-Si film formation which can allow light from the red to infrared wavelengths to be converted to electricity.”

By adding the CIM-1400 PECVD system to a turnkey line for tandem thin-film silicon PV modules, module power output will be improved by ~30% compared with a-Si thin-film photovoltaic modules, Ulvac said.  The CIM-1400 system provides a 10% reduction of the manufacturing cost per watt, according to Ulvac.

The tool simultaneously processes six of the standard Gen 5.5-size glass substrates, enabling a turnkey line to process a substrate every 90 seconds. With a cell conversion efficiency of 9% in the aperture area, an average module has a power output of 130 Wp. The tandem junction module has an annual power output of 32.5 MW, which compares with 25 MW for an a-Si module, the company said.  The tandem junction line with the new PECVD system has a 10% lower manufacturing cost per watt than an a-Si thin-film PV turnkey line. “Maximizing the investment productivity more than offsets the investment cost required for the CIM-1400 PECVD system,” Ulvac said.