Recycling rejected silicon wafers and dies for high grade PV cells

Abstract

The recent return of the US to the Paris Climate Accord, massive increase in solar panel production and energy storage solutions has resulted in pressure on supply for solar cell materials and recycling of panels installed in the 90's and beginning of the 2000's which have reached their end of life. In this work we focus on recycling silicon wafers and dies by stripping previous structures from the die using potent acids after which its base material is characterized and binned. We demonstrate the process for silicon p-type substrates where n-type doping is attained by using a simple solution of phosphoric acid, which is diffused into the substrate using a furnace thus creating a PN junction. In case the substrate is n-type it could be replaced by boric acid. This is followed by deposition of a conductive antireflective coating, bus bars and rear wafer metal coating. The initial demonstrated laboratory results indicate the feasibility of recycling wafers using simple low cost standard industrial methods.