A deeper look into CIGS cells.

[skids]

While DayStar seems to be racing faster towards rolling out large-scale production, HelioVolt seems to be the leader in the theory side of things. That may give them a competitive advantage in the long run, whenever a shakeout should occur. (However with demand so damn high and buyers taking anything they can grab, I think DayStar's short-term approach of just building the darn things will be viable for many years to come.) A while back they announced they "were the first" to fully understand exactly how CIGS cells work and model them, releasing an academic paper detailing some experimental results. A little more technical detail, but still in a vocabulary accessible to lay-people appeared last week in the EE Times, and I think gives a pretty accurate picture of the thin-film PV landscape as well.

HelioVolt Corp. (Austin, Texas) has developed a process based on rapid thermal annealing and anodic bonding that allows high-performance copper-indium-gallium-selinide (CIGS) films to be deposited on just about any substrate. Founder and photovoltaic pioneer Billy Stanbery claims the process can dramatically shorten manufacturing time and reduce the thermal budget by a factor of 10 to 100. The process could allow a new class of materials for building integrated photovoltaics that serve, for example, as a robust coating on external building materials or on interior furnishings like curtains, to turn buildings into self-powered photovoltaic plants.

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As a compound semiconductor, these systems have a direct bandgap, unlike silicon, and are therefore inherently more efficient at converting photons to electric current. "In 1983 I began work on CIS thin films," said Stanbery. "At that time it was our group at Boeing and another group at ARCO who were developing the technology."Shell inherited its current photovoltaic effort through a few corporate transfers, and due to the long development period by both the Boeing and ARCO groups, Stanbery is very familiar with Shell's approach. The exact nature of Honda's photovoltaic efforts is less well-known, he said.

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The rapid annealing of very thin films is the ideal way to create this intermixed phase material, which makes them ideal for high-throughput manufacturing. "There are several levels of advantages that you get out of this," Stanbery said. "On the first level, the films do not use very much material. That is significant because over half the cost of silicon solar cells is in the silicon itself. At the next level, you have a shorter value chain. The silicon cells have to be wired together and many additional packaging costs occur. With CIGS films, we eliminate most of that."

http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=180201674