Nonmetallic inclusions in solar cell silicon: Focusing on recycling of scraps

Lifeng Zhang, Eivind Øvrelid, Samuel Senanu, Benjamin Agyei-Tuffour, Adegboyega Nathaniel Femi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

10 Citations (Scopus)

Abstract

The solar grade silicon ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. The hard inclusions lead to wire breakages during the cutting of the ingot in wafers. The main kinds of inclusions found in solar grade silicon have been investigated using vacuum filtration: needle-like Si3N4 and lumpy SiC inclusions. Clusters of SiC inclusions and Si3N4 are also found. Surface observations of the scraps before polishing reveals that Si 3N4 inclusions are usually bigger and in some cases can be about a few millimeters. SiC inclusions are usually smaller, ∼200μm but can be ∼500μm in some cases. Inclusions observed after filtration are mainly SiC with diameters ∼10μm. Through the vacuum filtration, 99% inclusions can be removed 99%. The possible mechanisms of filtration are cake filtration for the larger sized Si3N4 and SiC inclusions and deep-bed filtration the SiC inclusions. For the directional solidified silicon ingot, an approximate distance of ∼10mm gave an encouraging cutoff thickness. The inclusions sizes were below 10μm.

Original languageEnglish
Title of host publicationProceedings of the 2008 Global Symposium on Recycling, Waste Treatment and Clean Technology, REWAS 2008
Pages1011-1026
Number of pages16
Publication statusPublished - 2008
Externally publishedYes
Event2008 Global Symposium on Recycling, Waste Treatment and Clean Technology, REWAS 2008 - Cancun
Duration: 12 Oct 200815 Oct 2008

Publication series

NameProceedings of the 2008 Global Symposium on Recycling, Waste Treatment and Clean Technology, REWAS 2008

Conference

Conference2008 Global Symposium on Recycling, Waste Treatment and Clean Technology, REWAS 2008
Country/TerritoryMexico
CityCancun
Period12/10/0815/10/08

Keywords

  • Foam filters
  • Inclusions
  • Silicon carbide
  • Silicon nitride
  • Solar cell silicon
  • Vacuum filtration

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