State-of-the-art growth of silicon for PV applications

Silicon is widely used in photovoltaic devices. This application requires strict control of the structure and impurity levels. Silicon must, therefore, be solidified using processes that give a minimum of impurity contamination and microstructural defects, as well as a planar solidification front to avoid microsegregation. Czochralski growth, and to some extent float zone crystallization, are processes used to obtain defect-free single crystals for advanced solar cell wafers, whereas the Bridgman process can be used for production of multicrystalline silicon for standard solar cells. Direct solar cell wafer solidification processes have also been developed and reached limited commercial use. The paper will review these silicon crystallization processes and discuss recent developments and trends.

► The article reviews silicon crystal growth techniques for photovoltaic applications. ► Monocrystalline PV silicon is primarily produced by Czochralski pulling. ► Multicrystalline PV Si is mainly produced by the VGF/Bridgman technique. ► Czochralski- and the VGF/Bridgman processes continue to be improved. ► New methods for higher purity, productivity and/or higher yield have also been commercialized.