Universidad Politécnica de Madrid

Instituto de energía solar


Solar silicon refinement


To meet the requirements of Photovoltaic applications, Silicon has to be ultrapurified to grades of 99.999999% (8N) or even beyond, in a process that accounts for between one fourth and one third of the total energy consumption in the production of a PV module, greatly impacting on the cost of the final product. The conventional ultrapurification process consists of converting metallurgical silicon in a volatile compound, typically trichlorosilane, that is purified by distillation, and recovered back as solid silicon in a chemical vapor deposition (CVD) reactor.

Our research relies on having a deep understanding of the silicon purification process. Through theoretical models describing heat transfer and thermodynamics, combined with computational fluid-dynamics modeling (CFD) and experimental research in a laboratory scale CVD reactor, energy saving strategies are identified and ways to implement them are pursued.

The Institute also supports initiatives to develop alternative purification processes that try to avoid the conversion to chlorosilane, following what is called a “metallurgical route”, with high potential for cost reduction. With an integral view of the complete value chain, from feedstock to solar cell, purity requirements are established, and ways to improve material quality are explored.



Contact person: Prof. Carlos del Cañizo

Selected publications

  1. A. Ramos; J. Valdehita; J.C. Zamorano; C. del Cañizo. "Thermal shields for heat loss reduction in Siemens-type CVD reactors". ECS Journal of Solid State Science and Technology. 5 - 3, pp. P1 - P7. The Electrochemical Society, 2016. (DOI: 10.1149/2.0171603jss)

  2. A. Ramos, A. Rodriguez, A. C.del Cañizo, J. Valdehita, J.C. Zamorano, A. Luque. "Heat losses in a CVD reactor for polysilicon production: Comprehensive model and experimental validation". Journal of Crystal Growth. 402, pp. 138 - 146. Elsevier, 2014. ISSN 0022-0248. (DOI:10.1016/j.jcrysgro.2014.05.020)

  3. G. del Coso, C. del Cañizo, A. Luque. "Chemical vapor deposition model of polysilicon in a trichlorosilane and hydrogen system". Journal of the Electrochemical Society. 155 - 6, pp. D485 - D491. Electrochemical Society, 2008. ISSN 0013-4651. (DOI: 10.1149/1.2902338)

  4. C. del Cañizo, A. Luque, J. Bullón, A. Miranda, J. M. Minguez, H. Riemann, and N. Abrosimov, "Integral procedure for the fabrication of solar cells on solar silicon", in 20th European Photovoltaic Solar Energy Conference and Exhibition, Barcelona, 2005, pp. 946-949..

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