Research on Recycling of Metal Si and Ag from Waste Photovoltaic Cells by Current Assisted Directional Solidification

Abstract

Waste crystalline silicon photovoltaic cells wafers have extremely high recycling value, and efficient recycling of them can not only reduce environmental pollution but also avoid the waste of resources. The current pyrometallurgical technology has a low recovery efficiency for high-value metals in battery cells and lacks an effective method for regulating element separation. In this paper, direct current (DC) assisted directional solidification is used to optimize the migration behavior of elements during solidification and promote the enrichment effect of metallic elements. The Joule heat effect of direct current is utilized to improve the diffusion behavior of elements at the solid-liquid interface fronts by introducing a micro heat source that acts directly on the solid-liquid interface. At a current of 40A, the proportion of enriched regions increased to 21%. By adjusting the action time of the current, the enrichment behavior of the elements in the final solidification zone was further optimized by ensuring the constant volume of bulk silicon, achieving micro area enrichment of metallic Ag. This method utilizes the micro-region heat source generated by direct current to modulate the purification effect of directional solidification, which is expected to achieve the efficient recycling of waste photovoltaic cells.

Keywords: Waste Photovoltaic Cells, Direct current, Directional solidification, Joule heat, Elemental enrichment