Appolon s recipe is for solar grade silicon ,not polysiliconSorry about this misinformation
here is the take
Polysilicon was originally designed to meet the demands of the electronic industry with purities between 9N to 11N depending on end usage. The Siemens process uses hydrochloric acid to dissolve MG-Si and produce a gas compound, trichlorosilane on a fluidized bed, then that gas compound is purified and finally reduced to solid silicon or Polysilicon. This process requires significant amounts of electrical energy (about 72 kWh per kg produced) and is potentially harmful to the environment because of the usage of chloride and silane in the process. Over the years, the Siemens process was optimized around producing 6N to 9N purity Si used in the solar industry and massive investments in commercial development lead to large plants being built. The main reason the chemical approach became the dominant process until now was the absence of alternatives to polysilicon in the early 2000s, when solar energy experienced it’s first boom. At that time, solar cells using metallurgically produce Solar Grade Silicon Metal were unable to reach the same levels of performance as those reached with polysilicon.
Metallurgically produced Solar Grade Silicon Metal (SoG-Si) has a purity of 5N+ with the main impurities being Boron, Phosphorus, Carbon and Oxygen. Contrary to chemical Solar Grade Si production (Siemens or FBR), the production of SoG-Si via metallurgical routes involves different liquid and solid phase processes, with at least 3 different purification steps (Cluster) needed to obtain solar requirements. Since the final purity of the product is adapted to solar application, CAPEX demands are reduced and after industrial scale optimization, operating costs (OPEX) will be significantly lower. Since 2007, many industrials have refined metallurgical Silicon into Solar Grade Silicon Metal (SoG –Si) via metallurgical processes and demonstrated that photovoltaic performances could be similar to performance attained using polysilicon.