Solar Energy

During the wafer manufacturing process crystallized ingots are first sawn into blocks and then into the wafer slices. Photo: SCHOTT/J. Meyer
Vera von Keller

From Silicon to a Module

Thanks to its joint venture with wacker Chemie AG, SCHOTT is now in an excellent position throughout the entire solar value chain.

Solar technology is considered to be a key technology for the 21st century. In recent years, however, the silicon that is urgently needed has become one of the world’s most sought-after raw materials. At the same time, this material is in short supply, because the installation of production capacities for hyperpure silicon has not been able to keep up with the boom in global demand. Solar companies that have been unsuccessful in securing long-term access to silicon deliveries are already finding it difficult to achieve their growth targets. And industry analysts do not expect this situation to ease up for quite some time. The production capacities for solar cells and modules are growing extremely quickly, especially in Asia.
Here, SCHOTT Solar has already made the right moves. The production sites for crystalline solar cells and modules in Germany, the Czech Republic and the U.S.A. have secure access to the materials they need and nothing is preventing the company from extending its manufacturing capacities even further.

In spring, WACKER SCHOTT Solar GmbH, with its headquarters in Jena, an industrial site in Thuringia, Eastern Germany, that is rich in tradition, became a supplier of wafers, razor-thin discs made of polycrystalline silicon and the product behind every shimmering blue solar cell. The joint venture between schott Solar and WACKER Chemie, the world’s second-largest provider of hyperpure silicon, combines the strengths of two market leading companies. WACKER Chemie, a leading specialist in the area of solar silicon, sees to it that this scarce raw material is available in sufficient quantities, while SCHOTT Solar ranks among the technology leaders in cells and modules.

As Professor Udo Ungeheuer, Chairman of the Board of Management at SCHOTT AG, puts it: ”By jointly addressing the incredibly dynamic growth market of photovoltaics, where annual growth rates are expected to range between 20 and 30 per cent, during the wafer value creation phase, we are considerably stronger than most of our competitors. The joint venture shall play a decisive role in strengthening SCHOTT Solar’s position as one of the world’s leading manufacturers of solar energy components.” After all, plans call for the annual manufacturing capacity for crystalline solar cells and modules at SCHOTT Solar to increase from currently 130 megawatts to 450 megawatts by 2010.
Following crystallization, the ingots are processed into individual silicon blocks that can weight up to 300 kilograms using a so-called ”squaring process”. Photo: SCHOTT/J. Meyer
Dr. Peter-Alexander Wacker, Chairman of the Board of Management of WACKER Chemie AG, also views the joint venture as a strategic challenge: ”Our forward integration into solar wafer production together with a strong partner is vital to our strategy of creating corporate value in the growth sector of photovoltaics,” he notes. For WACKER SCHOTT Solar, the starting point could not be better and includes ideal technological points of contact to the research and development department of SCHOTT Solar, a well-developed infrastructure, including enough space to build more production facilities and, last, but not least, broad support at the political level. Jürgen Reinholz, Minister for Economic Affairs in Thuringia, is very pleased with the new initiative that hopes are pinned on: ”This major investment strengthens Thuringia considerably as a top site for the solar industry in Europe,” he says.

The common goal is to manufacture and sell wafers of the highest quality. ”By the end of 2008, production capacity should reach approximately 120 megawatts per year and then increase to roughly one gigawatt per year by 2012,” explains Dr. Patrick Markschläger, Managing Director of WACKER SCHOTT Solar. Together with co-Managing Director, Axel Schmidt, he provided the impetus for investments of around 50 million euros for the initial phase of future manufacturing.
WACKER SCHOTT Solar GmbH is setting up a production facility for silicon wafers in Jena, Germany, for use in manufacturing solar cells. Photo: SCHOTT/J. Meyer
Process chain fully under control

Initially, SCHOTT will benefit from the premium quality wafers with its own manufacturing of cells and modules. However, already in 2008, efforts will be made to establish long-term business relationships aimed at selling wafers. ”SCHOTT Solar is currently our main customer, but we will be broadening our customer base in the years to come,” Markschläger notes. Users of wafer-based solar cells will also benefit from the close cooperation between WACKER and SCHOTT. ”SCHOTT already has the entire process chain that covers everything from silicon to modules completely under control. This results in cost savings and these wafers allow us to improve the quality of the cells even further,” explains Dr. Patrick Markschläger. Customers receive modules in which not only the cells, but also the wafers, satisfy the high technical standards for break resistance and efficiency. Here, WACKER SCHOTT Solar relies on proven technology developed by SCHOTT. The pilot installation has now been in operation for nearly two years. To begin with, individual chunks of hyperpure silicon are melted into a viscous mass at temperatures of around 1,400 degrees Celsius and then subjected to controlled cooling so that the crystalline structure of the up to 300 kilogram silicon blocks, or ingots, is perfectly suited for generating power from sunlight. Then, these multicrystalline silicon blocks are sawn into razor-thin, yet stable panes, or so-called wafers, at WACKER SCHOTT Solar’s own wafer manufacturing facility.

The advanced EFG process for wafer processing patented by SCHOTT is also part of the joint venture. A silicon film in the form of an octagonal hollow tube is pulled directly from the silicon melt, whose side lengths each make up one side of a wafer. Then, after cooling, a laser cuts out the wafers. Whereas with the conventional wire saw process, approximately half of the material used in wafer manufacturing is waste, only 10 percent is sacrificed with the EFG process, an aspect that saves resources. ”This raises high expectations,” says Markschläger, who feels confident the joint venture will offer a solid basis for further innovations.