We presented at the recent RadTech 2010 conference, a showcase for UV-curable coatings, inks, and adhesives. All technologies involved offer lower energy needs, faster throughput, lower volatile organic compound (VOC) releases, and/or lower-temperature operation by avoiding the need for heat-curing or long drying times. Many RadTech attendees were seeking new market opportunities for their technologies; and for many, solar headed their lists.
The photovoltaics section of the event featured a talk from Joshua Oliver of Sartomer, a division of oil giant Total, and a leading supplier of monomers, oligomers, and other raw materials for UV-curable products, including some used in solar applications. Joshua discussed the potential of UV-curable materials as encapsulant and barrier films, but explained that most UV-curable polymers can’t provide the barrier properties needed for solar applications. He added, however, that Sartomer found mixing UV-curable elements into a polymer similar to ethylene vinyl acetate (EVA) leads to a material that compares favorably to EVA in performance and durability after curing. Even so, UV-curable materials will have uphill battle to get into solar, however, unless they can eliminate the need for lamination altogether, as module manufacturers will be loath to add an additional curing tool to their lines.
Also on hand was transparent conductive film producer, Cambrios, which uses a UV-curable polymer as an overcoat to protect the silver nanowires that form its conductive layers. Teresa Ramos presented results showing that Cambrios could achieve sheet resistance as low as 50 ohm/sq with 96.6% light transmission, or 15 ohm/sq at 93.5% transmission, which signifies a performance improvement over incumbent transparent conductor indium tin oxide (ITO). Teresa noted that 10 ohm/sq to 20 ohm/sq is needed for inorganic thin-film PV users. However, when she discussed how Cambrios had achieved uniform properties over large areas – scaling up to large areas is one of the key challenges for non-active solar materials (see the report “Driving Down Solar Costs: Non-active Material Opportunities)” – the data were from films with 225 ohm/sq and 91% transmission. While Teresa was cagey in response to questions about its cost metrics (another critical factor for adoption) and commercialization plans, it appears that Cambrios still has some way to go before being able to address solar applications. That said, it remains a strong contender for transparent conductive films in display applications (see the March 22, 2010 LRNJ).
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