TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The silicon feedstock comprises (ppma) metallic elements (less than 150, preferably less than 50) and carbon (less than 100)    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The silicon feedstock comprises (ppma) metallic elements (less than 150, preferably less than 50) and carbon (less than 100) EXAMPLE - Commercial metallurgical grade silicon produced by carbothermic reduction in electric arc furnace was treated with a calcium silicate slag to remove mainly boron. Boron (1.2 ppma) was extracted from the molten silicon to the slag phase. The silicon was solidified with very pure silicon crystals while impurities stayed in the melt until most of the silicon was solidified impurities ended up on the grain boundaries in the solidified silicon. The solidified silicon was subjected to acid leaching where the inter-granular phases was attacked and dissolved together with the impurities. The remaining undissolved granular silicon was melted and further refined to adjust the composition before crusting and sieving to obtain the silicon feedstock for solar grade silicon. Two charges of silicon feedstock were produced. Silicon feedstock produced was used to produce two directionally solidified silicon ingots. Commercial multi-crystalline silicon wafers were used as a reference. A crystalox DS250 furnace was used for producing the ingot. A circular quartz crucible with an inner diameter of 25.5 cm and 20 cm height capable of containing feedstock (12 kg) was used. The grown ingots were squared to 100 cm2 and 156 cm2 blocks and then sliced into wafers. From these blocks, a large number of wafers with thickness of 300 - 330 microns were produced for cell processing. The resulting solar cells were fabricated by POCl3 emitter diffusion, PECVD SiN deposition and edge isolation by plasma etching. The front and back contacts were made by screen printing and then firing through. The efficiency of the fabricated test/comparative solar cells was found to be 14.8/14.6.