Recycling solar-grade silicon from end-of-life photovoltaic modules by Al-Si solvent refining

Abstract

Abstract The development of the solar market is fast in the past decades, and the number of solar module installations is huge. The solar modules have a lifetime of about 25 years and should be recycled after that. The Al-BSF module is the first kind of large-scale installed module and will come to its end of life in the next few years. The recycling of silicon in the Al-BSF module is investigated in this work. The components of the module are separated, and the silicon in the module is collected and then purified to remove boron and phosphorus by Al-Si solvent refining. It is found that impurity boron and phosphorus in this work have little influence on the solidification behavior of the hyper-eutectic Al-Si melt. The Al-Si solvent refining removed impurity elements boron and phosphorus in the silicon. Kinetics has a great effect on boron and phosphorus removal, and boron and phosphorus contents in purified silicon decrease with decreasing cooling rate. The boron and phosphorus contents in silicon are lowered to 0.28 and 0.03 ppmw respectively after two times of Al-Si solvent refining with the cooling rate of 5.55*10− 4 K/s, and it meets the requirement of solar-grade silicon.