Recycling rejected silicon wafers and dies for high grade PV cells

TL;DR

This paper presents a low-cost, industrially feasible method for recycling silicon wafers and dies from old solar panels, enabling the creation of high-grade photovoltaic cells through chemical stripping and doping techniques.

Contribution

It introduces a novel recycling process that restores silicon wafers from end-of-life panels into functional PV cells using simple chemical and thermal treatments.

Findings

Successful doping of recycled wafers with p-type and n-type materials.

Feasibility of creating PN junctions on recycled substrates.

Use of standard industrial methods for wafer recycling.

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.