ZSW touts flexible CIGS from a single tool

Researchers at the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) say they have combined “the most important production steps” of making flexible CIGS solar modules into a single tool.

May 26, 2011 – Researchers at the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) say they have simplified manufacturing of flexible CIGS solar modules by combining “the most important production steps” into a single tool, instead of each layer deposited in separate systems.

The group claims continuous web coating of CIGS on a temperature-resistant plastic film (25μm thick × 30cm wide polyimide substrate) on a 12m system, achieving 10.2% efficiency. (Other firms working on flexible CIGS tout around 11% efficiency; just days ago Swiss scientists topped 18% conversion efficiency.)

“All coating steps take place simultaneously in the same vacuum,” says Michael Powalla, head of ZSW’s photovoltaics division, in a statement. The molebdynum back contact is applied at one end of the system via cathode sputtering, and co-evaporation of the CIGS absorber and deposition of the transparent front contact layer “are located elsewhere in the system,” he explains. The system currently can deposit the back contact, the four absorber elements, and zinc oxide window layers; a new buffer layer is in development for future integration, and eventually so will be a monolithic cell interconnection, ZSW says.

There’s a great deal of discussion about the pros/cons of thin-film PV (like CIGS) vs. crystalline silicon solar PV technologies. Moving thin-film onto plastic substrates, though, offers great potential for applications requiring flexibility and light weight, such as buildings, vehicles/aircraft, and even clothing. Modules with the solar foil bonded to a glass substrate would weigh half as much as standard two-panel modules for rooftop systems.

The work on the web-coating flexible CIGS system was backed by Germany’s Federal Ministry for the Environment, Nature Conservation and Reactor Safety (BMU) through the CISROLL investment project.

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Left: Overall view of the web-coating system. Right: Unrolling of the plastic film. (Source: ZSW)



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