Solar cells from upgraded metallurgical-grade silicon purified by metallurgical routes

We report a combination of metallurgical routes intended to improve the purity of metallurgical grade silicon (MG-Si) for solar cell fabrication. Initially, MG-Si was submitted to vacuum degassing (VD) by means of an electron-beam to reduce the impurities represented by chemical elements with high vapour pressure. This was followed by preparing a monocrystalline ingot using the Czochralski (CZ) growth technique. The impurity concentration was measured by glow discharge mass spectrometry. The results demonstrate that a procedure combining VD with CZ growth has the potential to improve the purity of MG-Si to greater than 99.999%. Solar cells made by different processes were used for the sake of comparison and also to verify the quality of the silicon wafers prepared by the combination of VD with CZ techniques. The results showed the potential to reach efficiencies necessary for the production of commercial solar panels.