How do Impurity Inclusions Influence the Mechanical Properties of Multicrystalline Silicon?

Orellana Pérez, T. and Tejado Garrido, Elena María and Funke, V.C. and Fütterer, W. and Riepe, S. and Möller, H.J. and Pastor Caño, Jose Ignacio (2015). How do Impurity Inclusions Influence the Mechanical Properties of Multicrystalline Silicon?. "International Journal of Metallurgical & Materials Engineering", v. 1 ; pp. 1-11. ISSN 2455-2372. https://doi.org/10.15344/2455-2372/2015/101.

Description

Title: How do Impurity Inclusions Influence the Mechanical Properties of Multicrystalline Silicon?
Author/s:
  • Orellana Pérez, T.
  • Tejado Garrido, Elena María
  • Funke, V.C.
  • Fütterer, W.
  • Riepe, S.
  • Möller, H.J.
  • Pastor Caño, Jose Ignacio
Item Type: Article
Título de Revista/Publicación: International Journal of Metallurgical & Materials Engineering
Date: 2015
ISSN: 2455-2372
Volume: 1
Subjects:
Freetext Keywords: Failure analysis, Fracture, Impurity inclusions, Mechanical properties, Multicrystalline silicon
Faculty: E.T.S.I. Caminos, Canales y Puertos (UPM)
Department: Ciencia de los Materiales
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

The purpose of this research is to characterise the mechanical properties of multicrystalline silicon for photovoltaic applications that was crystallised from silicon feedstock with a high content of several types of impurities. The mechanical strength, fracture toughness and elastic modulus were measured at different positions within a multicrystalline silicon block to quantify the effect of impurity segregation on these mechanical properties. The microstructure and fracture surfaces of the samples was exhaustively analysed with a scanning electron microscope in order to correlate the values of mechanical properties with material microstructure. Fracture stresses values were treated statistically via the Weibull statistics. The results of this research show that metals segregate to the top of the block, produce moderate microcracking and introduce high thermal stresses. Silicon oxide is produced at the bottom part of the silicon block, and its presence significantly reduces the mechanical strength and fracture toughness of multicrystalline silicon due to both thermal and elastic mismatch between silicon and the silicon oxide inclusions. Silicon carbide inclusions from the upper parts of the block increase the fracture toughness and elastic modulus of multicrystalline silicon. Additionally, the mechanical strength of multicrystalline silicon can increase when the radius of the silicon carbide inclusions is smaller than ~10 µm. The most damaging type of impurity inclusion for the multicrystalline silicon block studied in this work was amorphous silicon oxide. The oriented precipitation of silicon oxide at grain and twin boundaries eases the formation of radial cracks between inclusions and decreases significatively the mechanical strength of multicrystalline silicon. The second most influencing type of impurity inclusions were metals like aluminium and copper, that cause spontaneous microcracking in their surroundings after the crystallisation process, therefore reducing the mechanical response of multicrystalline silicon. Therefore, solar cell producers should pay attention to the content of metals and oxygen within the silicon feedstock in order to produce solar cells with reliable mechanical properties.

More information

Item ID: 40720
DC Identifier: http://oa.upm.es/40720/
OAI Identifier: oai:oa.upm.es:40720
DOI: 10.15344/2455-2372/2015/101
Official URL: http://www.graphyonline.com/archives/IJMME/2015/IJMME-101/
Deposited by: Memoria Investigacion
Deposited on: 03 Jun 2016 15:37
Last Modified: 24 Sep 2018 06:59
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