Right now, thin-film solar cells represent only a fraction of the sales generated by their big sibling, silicon-based solar cells. But several recent news items suggest that thin-film technology might be poised to soon step out of that long shadow.

Earlier this week, HelioVolt, a private thin-film solar company specializing in copper-indium-germanium-selenide (CIGS) solar cells, announced that it had raised $77 million in a second round of financing. The money will fund construction of a factory capable of producing 20 megawatts of solar panels by 2009. That's only slightly less than the $100 million that Nanosolar, another private thin-film company, announced it would be pouring into a 430 MW production facility late last year.

HelioVolt is particularly noteworthy because it claims that its cells have an efficiency rating of 10% to 12%. That's still considerably less than silicon-based solar cells, which have efficiency ratings of between 16% and 22%. But because thin-film cells don't rely on silicon, and can be relatively easily manufactured (once the kinks are worked out of the system), they're expected to be cost-competitive with silicon solar cells for an increasing number of applications.

This will be especially true if HelioVolt can make good on its promise to print its CIGS material onto glass -- an application that would allow windows and other building material to perform double duty as both solar collectors and structural platforms.

HelioVolt is not alone in this field. Yesterday, Norsk Hydro (NYSE:NHY) announced that it would be investing an additional $10 million in Ascent Solar Technologies (NASDAQ:ASTI). And earlier this year, Suntech Power (NYSE:STP) declared it would begin building a new 50 MW thin-film manufacturing facility in Shanghai, while Applied Materials (NASDAQ:AMAT) revealed it would be supplying the equipment for a 250 MW thin-film facility being developed in India by Moser Baer. Still other companies, including Miasole, Konarka, United Solar Ovonics (a subsidiary of Energy Conversion Devices (NASDAQ:ENER)), and Innovalight -- a holding of Harris & Harris (NASDAQ:TINY) -- are also making great strides in this field.

With all this activity, I'm betting that thin-film solar technology won't remain the proverbial 98-pound weakling to its silicon-based sibling much longer. Investors in more traditional silicon-based solar companies might want to take notice of thin film's growing strength. Those who've had sand (or in this case, silicon) kicked in their face for so long just might have a little extra motivation to return the humiliation.

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Fool contributor Jack Uldrich owns stock in Suntech and Harris & Harris, both Motley Fool Rule Breakers picks. The Fool's strict disclosure policy is the hero of the beach.