Recycling of diamond-wire sawing silicon powder by direct current assisted directional solidification

Abstract

As the unavoidable by-products in the production of solar cells, the recycling and reuse of diamond-wire sawing silicon powder (DWSSP) have always been a key issue in the solar energy industry. However, until now, there is no effective method to achieve effective recovery of high-purity silicon. In this work, a new method was proposed to achieve the recycling of DWSSP. Direct current, as an external means, was introduced into the recycling process of DWSSP, and its influence mechanism on impurity removal process was also discussed. By optimizing the local temperature gradient at the front of the Solid-Liquid interface, and the impurity diffusion behavior at the front of the interface was improved. After purification, the impurity content in the silicon ingot is reduced significantly. Among them, Al, as the main metal impurity element was reduced to less than 5ppmw (from 13580ppmw), and Ni (80.78ppmw), Fe (57.60ppmw), Ti (5.79ppmw), etc. decreased to less than 1ppmw. This work improved the purification efficiency of DWSSP, and put forward an optimized recycling method, which is expected to realize the direct reuse of DWSSP in the photovoltaic industry.