Solar cells made of a semiconductor material containing copper, indium, gallium, and selenium (CIGS) can be almost twice as efficient as amorphous silicon, but are more sensitive to moisture and so require better protection from the elements. Many CIGS manufacturers already have come up with manufacturing processes to deposit the compound onto rolls of pliable metal foil or plastic. The companies say they can make solar panels faster using this roll-to-roll process; achieving higher production volumes is crucial for reducing manufacturing costs. But they have relied on glass for the front sheet because of a lack of suitable plastic. Aside from CIGS solar-panel makers, 3M also is targeting developers of cadmium-telluride and organic thin films, DeScioli says.
Minnesota-based 3M set out to develop a more durable front casing, and the result is a plastic film that is 23 micrometers thick, much thinner than the 3,000-micrometer glass typically found on solar panels today, DeScioli says. The company uses fluoropolymer because the material doesn’t allow water to seep through easily, and it is resistant to high temperatures and ultraviolet radiation. 3M also engineered the film to prevent it from reflecting much sunlight. 3M says its film can achieve water vapor transmission rates of less than 0.0005 grams of water per square meter per day. Other front barrier films can let in hundreds of times more moisture.
DeScioli says the film can be laminated in the same roll-to-roll process used to deposit thin-film semiconductors, and that can shave production costs. Flexible solar panels also can be larger than glass panels because the flexible variety doesn’t require the support of a racking system and can be easier to transport. The time and costs for assembling an array of large panels can be significantly less than putting together many small panels, he says.
“The primary value of our film is, it enables our manufacturers to make larger modules with the roll-to-roll process,” DeScioli says. He says that while the material itself will not cost less than glass, it will reduce overall costs by saving on manufacturing and installation.
3M is making the film at a pilot production line and plans to mass-produce it next year. The company says it has lined up customers, but DeScioli declines to disclose them.