Cadmium Telluride Solar Cells Breakthru in the Works

First Solar appears to be leading the way in development of cost effective solar cells. According to the article at IEEE they are claiming their

product has three massive cost benefits. Its ­active element is just a hundredth the thickness of the old standby, silicon; it is built on a glass substrate, which enables the production of large panels; and manufacturing takes just two and a half hours—about a tenth the time it takes for silicon equivalents.

Apparently the order books are full, new production capacity is being built and the stock is soaring.

Plus they are keeping critical steps in their process secret and refuse to talk to the press. Remembering back to my IP class the fact that trade secrets offered potentially so much longer protection that patenting was revelation to me.

Nevertheless, it is still possible to uncover some of the details of First Solar’s growth process. ... an elemental vapor deposition process that takes place in four chambers.

Glass is placed on rollers and fed into the first chamber, where it is heated to 600 °C. Then it is transferred into the second chamber, which is full of cadmium sulfide vapor, formed by heating solid CdS to 700 °C. The vapor forms a submicrometer deposit on the glass as it moves through this cloud, after which a similar process in a third chamber adds a layer of micrometers-thick CdTe in about 40 seconds. Then a gust of nitrogen gas rapidly cools the panels to 300 °C in a fourth chamber, strengthening the material so that it can withstand hail and high winds.

for the rest of the story

IEEE also supplies these references

Solar Cells Inc. describes the details of its elemental vapor process in its 1993 report “Fabrication of Stable Large-Area Thin-Film CdTe Photovoltaic Modules,” which is available at http://www.osti.gov/bridge/product.biblio.jsp?osti_id=10181903.

Get information about inverted triple-junction technology in “High-Efficiency GaInP/GaAs/InGaAs Triple-Junction Solar Cells Grown Inverted With a Metamorphic Bottom Junction,” Applied Physics Letters, 91 023502, 2007.

For comparisons between CdTe and CIGS manufacturing, see Michael Powalla and Dieter Bonnet’s paper “Thin-Film Solar Cells Based on the Polycrystalline Compound Semiconductors CIS and CdTe” published in Advances in OptoElectronics, 2007, available free of charge at http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/97545.