SGL Carbon has been a partner of the photovoltaics industry since its early beginnings in the 1990s. We provide you with all graphite materials needed to grow either mono- or multi crystalline solar wafers and have decades of experience in materials based process improvements.
Contact one of our experts using the form below if you want to improve yield, quality or energy consumption in your process.
Furthermore, we can support you with engineering and calculation in the development, analysis and optimization of your products and processes.
Mono silicon crystal growth
The best conversion efficiencies of sun-light into electricity of commercial solar cells can be obtained by mono crystalline based silicon solar cells. The silicon wafers are cut out of silicon ingots grown by the Czochralski (CZ) method.
The crystal growing furnaces used for this process operate at high temperatures of around 1500°C and are equipped with an SIGRAFINE® isostatic graphite hot zone consisting of a heater, outer tubes and rings, quartz crucible susceptor and other graphite items depending on the particular design.
The graphite hot zone has to be thermally insulated. For this purpose, SGL Carbon offers different graphite insulation materials: SIGRATHERM® graphite soft felt, SIGRATHERM graphite rigid felt and SIGRAFLEX® flexible graphite foil can be used as well as combination materials of soft or rigid felt and graphite foil to even improve the performance. Additionally, SIGRAFLEX high-purity foil and sheets made from expanded natural graphite can also be used as high-performance heaters or heat shields. And SIGRAFLEX flexible graphite is also often used in combination with SIGRATHERM rigid felts, SIGRABOND® carbon fiber-reinforced carbon and SIGRAFINE artificial graphite.
SGL Carbon offers all of the materials needed from one source and has decades of experience in finding suitable solutions.
Multi silicon crystal growth
Multi-crystalline silicon is produced by the directional solidification (DS) method. In the past it has been the main material for solar cells due to lower manufacturing costs than Mono crystalline silicon growth.
However, solar cells made from Multi-Si have disadvantages in photoelectric conversion efficiency, mainly because of structural defects known as grain boundaries and higher impurity levels than CZ mono silicon.
The DS silicon growth process is carried out in rectangular quartz crucibles that are supported on the bottom and the side walls by graphite plates. All DS furnaces use side heaters and often top and/or bottom heaters made out of graphite. Additionally, most companies use a top cover plate that is commonly made out of SIGRABOND carbon-fiber reinforced carbon (CFRC). The furnace insulation is typically based on SIGRATHERM graphite rigid felt.
Materials
Benefit from the high purity of our graphites and insulation materials - developed especially for challenging processes like mono and multi silicon crystal growing.
Our Product Finder for SIGRAFINE Fine-Grain Graphite can help you pre-select the appropriate graphite grades for your application.
