Thin-film Technology

Sunlight releases electrons in the semiconductor layer of the ASI solar cell. This layer is divided into stripes that form solar cells and are connected electrically in series. Photo: SCHOTT/J. Meyer
Vera von Keller

Razor-Thin Solar Radiation Converters

High-capacity thin-film solar modules expand the planning horizons for architects and project developers.

The roof of the aboveground subway station Stillwell Avenue in Brooklyn, New York, fulfills several functions. The airy steel glass construction protects passengers from the wind and rain and shields the surrounding neighbors from the noise of the platform. ”One innovative aspect is that shadow donors integrated into the roof simultaneously produce two-thirds of the electricity the subway station needs,” says Dr. Lawrence L. Kazmerski, a respected expert on photovoltaics at the National Renewable Energy Laboratory in Golden, Colorado. This was made possible by the fact that 5,500 square meters of thin-film modules (= 2,800 modules) from SCHOTT Solar were integrated into the bold glass mantle. As this example demonstrates, when glass is combined with integrated system solutions, this opens up extraordinary design possibilities. The up-and-coming discipline of solar architecture in particular is relying on glass elements in facades or on top of roofs to offer futuristic system solutions that create the link between esthetics and increasing demands for climate-compatible power generation.
Futuristic technology of thin-film solar modules – e. g. at »Stillwell Avenue Station« – combines customized designs of facades and roofs with environmentally friendly generation of electrical power. Photo: SCHOTT/P. Heilmann
Being able to offer project developers, architects or building owners high quality solutions requires decades of in-depth technological know-how. Here, SCHOTT has been manufacturing thin-film modules in pilot series and limited-lot volumes in Putzbrunn near Munich since 1988. This also resulted in the colorful accent in the facade of the SCHOTT headquarter building in Mainz. Thin-film modules combined with Artista® flat glass were integrated into the paneling of the staircase. With growing demand, sufficient volumes of modules must be available on short notice, to be able to mount thin-film modules on a facade imprinted with graphic elements so that the transparent glass fronts can produce electricity virtually invisibly or so that shadow donors on light-flooded roof surfaces can simultaneously produce electricity, for example. For this reason, the infrastructure for mass production of asi thin-film modules was established in Jena in only 15 months time.
Thin-film modules were integrated into this staircase designed with Artista® colored glass. Photo: SCHOTT/A. Sell
ASI solar cells are panes of glass upon which silicon has been deposited in razor-thin layers that convert sunlight directly into electrical power. Now, 180 employees can work around the clock, seven days a week, to produce a total of 33 megawatts per year. When the plant was inaugurated last November, Professor Udo Ungeheuer, Chairman of the Board of Management of SCHOTT ag explained: ”By taking this strategic step forward, we are establishing a second source of revenue for our photovoltaic activities, next to our wafer-based technology, and at the same time improving our position as one of the world’s leading manufacturers in the field of thin-film technology.”

ASI thin-film modules set new standards, particularly with respect to efficiency. They require substantially less silicon, which saves costs. Besides, even with a less favorable roof orientation or slope and in warmer regions, they produce a higher energy yield than crystalline modules. This definitely pays off. ”A very large share of our manufacturing capacity through the year 2010 has already been bought,” says Dr. Robert Kuba, Managing Director of Thin-Films at SCHOTT Solar, who views the future rather optimistically. ”By 2010, we plan to expand our production capacities in the area of thin-film to 100 megawatts per year,” he adds.