Recent Patenting Activities in Low-Cost Silicon Raw Materials for Silicon Solar Cells

Xin      Gu; Deren      Yang; Tingting      Jiang; Xuegong      Yu; Duanlin      Que

Abstract

For the last decades, numerous researches and patents are focused on developing novel refining processes of low-cost silicon. In this paper, patents that reveal different refining methods including chemical routes, metallurgical routes and other promising routes are reviewed respectively, and the detailed processes together with their pros and cons are demonstrated according to their basic principles. Based on different processes used for silicon production, the corresponding techniques of fabricating silicon ingots and solar cells are also introduced.

Keywords: Low-cost silicon, refining, impurity, chemical route, metallurgical route, solar cell, fabricating silicon, fossil fuels, solar energy, pn junction, photovoltaic effect, p-type semiconductor, n-type semiconductor, Earth's crust, solar grade (SOG) silicon, electronic grade polysilicon, solar cell fabrication, halogen silane, chemical vapor deposition (CVD), Siemens process, fluidized bed reactor, Union Carbide, Ethyl Corporation's processes, material recycling, Czochralski (Cz) growth, directional solidification, crucible, surface area, gas reactant, vapor-to-liquid deposition, high purity graphite reactor, polysilicon, orthoethylsilicate or tetraethoxysilane, carbothermic reduction, hydrometallurgical refining, slagging, Elkem's slag-based pyro-metallurgical refinement technique, Elkem's products, Zone melting, zone refining, electromagnetic induction, vacuum evaporation, wet hydrogen atmosphere, efficiency, solidification, horizontal zone melt refining technique, solid-liquid interface, segregation coefficients, rejection' principle, crystallization front, surface oxidization, Al-Si alloy, Electrometallurgy, aluminothermic, electrolysis, exothermic chemical reactions, Calisolar, silicon wafers, casting growth, Cz-silicon ingots, mass ratio, gallium, photovoltaic, surface damage gettering, nitridation/oxidation treatment, ohmic contact, epitaxial silicon film, silane-related compound