Thin-film photovoltaics (TFPV) have many things going for them, especially in the cost and mass departments.
TFPV costs less than conventional crystalline silicon approaches, especially if it can be manufactured using roll-to-roll (R2R) processes and equipment, and it weighs significantly less than its Si counterpart. Plus, TFPV proponents believe they have other advantages, such as transparency, flexibility, and additonal functional atttributes. Despite low conversion efficiencies compared to crystalline silicon, TFPV continues to gain market share.
NanoMarkets has a report on thin film, organic and printable PV, set for August publication. In advance of that, Lawrence Gasman recently posted a good overview of the TFPV space on the NanoMarkets TOP blog, entitled "Thin Film Photovoltaics: How, Where and Why." Here's an excerpt from Lawrence's discussion of uncertainties and challenges (although I suggest you read the whole piece):
"The climate in the PV industry these days---and especially in the TF PV sector---is extremely bullish and understandably so. Sales are booming, investment is pouring in. Many of the veterans of this industry began their careers in PV and are nearing retirement. They now see an opportunity to cash in. There are, however, considerable uncertainties and challenges for TF PV that are often papered over in the more breathless accounts of what the PV industry will become. Roughly speaking, these can be categorized into three areas (1) broad socioeconomic factors, (2) materials and production issues and (3) productization issues."
One company dealing with all three areas and pushing TFPV toward high-volume manufacturing is Santa Clara-based Miasole (pronounced like a fake French word, "me-ah-soul-lay"). Company president David Pearce presented an overview/progress report at the Emerging Technologies TechXpot at Semicon West. Although a PDF of his presentation can be found here, his full talk included some recent data/info he deigned not to include in the available version of the preso.
Miasole's approach is to manufacture CIGS (cadmium-indium-gallium-selenide) thin-film solar cells on flexible stainless-steel foil using internally designed vacuum-deposition (sputtering) R2R tools. These are big-ass systems, capable of processing seven different film layers on meter-wide coils of foil, which can reach 5 km in length, at a line-speed of 2 feet per minute. I know the measurements are mixed metric-English, but you get the picture---the output is enormous. Pearce said one production line could produce 250,000 square meters of PV per year. He also extolled the deposition virtues of the sputterers, saying they are very good at making films quite uniform over large areas.
The process IP involves a dual-cylindrical magnetron scheme; 40 separate magnetrons put down film stacks tens of micron thick, at that 2 ft/min speed. The company has two working systems on the floor of its San Jose factory, with components coming for the third and fourth tools, according to Pearce.
Among thin films, CIGS has no peer when it comes to demonstrated conversion efficiency. Pearce said it has reached 19.5% in an NREL lab, which is only several percentage points behind conventional silicon. In terms of efficiencies achieved outside the lab, he said Miasole has hit 14% on a small-scale line, better than 10% on a full-scale pilot line, and between 7% and 8% on the production coating tools that are still ramping---which represents a jump of 3 points in the past 3 months, with more process refinements to come.
When asked about development/production bottlenecks, akin to the problems with furnaces in some silicon PV lines, he said "the CIGS itself is the bottleneck," since it's tricky to "get the material to deposit correctly and to get the junctions properly formed." As for the possible scarcity of indium itself, since some solar soothsayers warn of an impending shortage, Pearce poo-pooed their cautionary prognostications, saying the key element was abundant in the earth's crust.
Pearce said Miasole's goal is to reach grid-parity (10 cents/kwH) by 2010. He also mentioned that the company is working with the "largest U.S. membrane roofing manufacturer," to explore how Miasole's cells could be integrated into roof material. He also cited a price tag of $25 million per TF CIGS production line, as measured by an investment per 100-MW capacity. That's significantly less than the $250 million or so that it takes to build a large silicon-based-cell facility.
Miasole may not be out of the woods yet, but it certainly seems to have a good shot at being one of the first to market among emerging players attempting to deliver a mass-produced, flexible, CIGS-based TFPV product. (last graf revised 29 Sept.)
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