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2003 R&D 100 Award Winner

High-Rate Vapor Transport Deposition for CdTe PV Modules

Developers: Dr. Harin Ullal, Ken Zweibel, and Dr. Bolko von Roedern, National Renewable Energy Laboratory; Dr. Rick Powell and Dr. Peter Myers, First Solar, LLD

A module per minute. First Solar's automated, non-stop, continuous-feed production line can crank out one PV module per minute — and these are 60 cm x 120 cm, high-quality modules made of thin-film cadmium telluride (CdTe) and cadmium sulfide (CdS). How is it done? Soda-lime glass is fed into vacuum deposition chambers where a layer of CdTe is deposited on the glass followed by a layer of CdS. The modules are then laser-scribed, metalized, and encapsulated in ethyl vinyl acetate, and then another layer of soda lime glass.

The enabling core of this process is the award-winning high-rate vapor deposition technology (HRVDT) developed by First Solar and NREL. This is a deceptively simple deposition technology that can deposit a thin, uniform layer of CdTe or CdS over the glass substrate in less 40 seconds — a deposition rate 3 to 4 orders of magnitude greater than rival thin-film photovoltaic technologies.

This is the world's first such mass-production method for making polycrystalline thin-film modules. In its first year of production, the technology has helped First Solar cut the price of PV modules to $2.50 per watt. The potential is even greater. A second-generation production line now under construction promises to lower the price by nearly another 50% in the next three years.