PHOTOVOLTAICS TODAY

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The most promising of the new technologies at this point is called thin film. Unlike the single-crystal process, in which the wafer is physically carved from a solid block of sili con, the thin-film process turns the silicon into a gas that is deposited as a vapor on an inexpensive backing, such as window glass. The glass is thus coated with an extremely thin layer of amorphous silicon that serves as the semiconductor base for the solar cell.

Thin-film technology's main advantage is that it uses 1/300 the amount of silicon that's needed to make a single-crystal cell. Now, raw silicon itself isn't expensive (beach sand is made of it), but it's worth about $300 per pound by the time it's been refined sufficiently to make a solar cell. The savings, then, are pretty obvious.

Another advantage to thin films is that they offer a greater latitude in the types of materials that can be used to fabricate them. Until the advent of thin films, solar technology was pretty much limited to a small group of semiconductor elements—silicon was the leading contender. With the new method of cell production, however, engineers are now free to work toward developing the most cost-effective combinations possible.

This effort is already paying off. Bill Yerkes, a pioneer in photovoltaics and the founder of what is now ARCO Solar, recently announced the development of a thin-film solar cell using cadmium telluride. Yerkes's new cell contains absolutely no silicon, and he claims it will cost less to manufacture yet will perform better than amorphous silicon cells. By the time you read this, his new venture—Industrial Design, Inc., of Chattsworth, California—will be manufacturing cadmium telluride solar cells on a production basis. [EDITOR'S NOTE: An article on Yerkes's PV-equipped mobile home appeared in MOTHER N0. 82. For information on ordering this and other back issues mentioned above, turn to page 108.]

As 1990 approaches, there will be a gradual shift in the consumer market from single-crystal products to thin-film designs. This metamorphosis means that good deals will abound during the transition period. All in all, now is a great time to invest in your future—by investing in photovoltaics.

ARCO SOLAR'S GENESIS

The industry's first high-powered thin film photovoltaic module was unveiled recently by ARCO Solar, the world's leading producer of PV power. The module is named, appropriately enough, Genesis. This one-foot-square panel is made with an amorphous silicon-hydrogen compound by an advanced thin film technique. The introductory module, which generates 5 watts at 12 volts, is targeted at recreational vehicle owners, who previously have had to live with panels that really were too large and powerful for their occasional needs.

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