SP1 Silicon feedstock

CRYSTALCLEAR is dedicated to crystalline silicon photovoltaic (PV) modules. Modules form the heart of any PV system and crystalline silicon technology has a global market share of over 90%, illustrating the importance of the CRYSTALCLEAR working area. The solar cells in such modules are made of very high purity silicon, the so-called feedstock. Silicon is, after oxygen, the most abundant element in the crust of the earth. It is produced in large quantities by reaction of quartz (silicon oxide) and cokes (basically carbon) at high temperature in electric arc furnaces.

For solar cells (as well as for microelectronic chips) a high grade of silicon is required. Only then can the electrical properties be controlled sufficiently to allow use in devices. It is custom to speak about "solar grade" and "electronic grade" material. The production of this high-purity silicon requires advanced equipment, is expensive and energy-intensive. Until now, the PV industry has used surplus and "off-spec" electronic grade silicon from the microelectronics industry. This is however an inherently limited source, which can no longer fulfill the needs of the rapidly growing (recently by 30-40% per year) PV industry. Assuring security of silicon supply has therefore become one of this industry's main challenges.
 
Worldwide, several alternative manufacturing methods for high-purity silicon are under development. These methods aim at combining sufficient quality for use in high-efficiency solar cells with reduced cost compared to today's mainstream electronic grade silicon production. One of the main aims of Subproject 1 in CRYSTALCLEAR is to test silicon from pilot production of these alternative methods on its suitability for use in advanced solar cell production. After initial screening on some basic properties the material is tested "in real life" by several industrial and institute partners, and feedback is provided to the manufacturer.
 
The other major aim of SP1 is to gain better scientific understanding and practical know-how on solar grade silicon. In SP1 available materials are studied in detail, but also model materials are produced and investigated, with emphasis on the impact of chemical impurities in the silicon on solar cell performance. This will result in well-founded specifications for major impurities in solar grade silicon and will allow design of optimum processes for silicon production as well as dedicated cell manufacturing processes.