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Numerical modelling and validation of thermally-induced spalling

Berardone, Irene and Kajari-Schröder, Sarah and Niepelt, R and Hensen, J and Steckenreiter, V and Paggi, Marco Numerical modelling and validation of thermally-induced spalling. Energy Procedia, 77. pp. 855-862. ISSN 1876-6102 (2015)

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In order to reduce the silicon consumption in the production of crystalline silicon solar cells, the improvement of sawing techniques or the use of a kerf-less process are possible solutions. This study focuses on a particular kerf-less technique based on thermally-induced spalling of thin silicon layers joined to aluminum. Via a controlled temperature variation we demonstrate that it is possible to drive an initially sharp crack, introduced by laser, into the silicon substrate and obtain the detachment of ultra-thin silicon layers. A numerical approach based on the finite element method (FEM) and Linear Elastic Fracture Mechanics (LEFM) is herein proposed to compute the Stress Intensity Factors (SIFs) that characterize the stress field at the crack tip and predict crack propagation of an initial notch, depending on the geometry of the specimen and on the boundary conditions. We propose a parametric study to evaluate the dependence of the crack path on the following parameters: (i) the distance between the notch and the aluminum-silicon interface, (ii) the thickness of the stressor (aluminum) layer, and (iii) the applied load. The results for the cooling process here analyzed show that ΔT >43 K and a ratio λ=0.65 between the thickness of the stressor layer and the distance of the initial notch from the interface are suitable values to achieve a steady-state propagation in case of a ratio λ0=0.115 between the in plane thickness of the silicon substrate and the aluminum thickness, a value typically used in applications.

Item Type: Article
Identification Number: 10.1016/j.egypro.2015.07.121
Projects: ERC StG CA2PVM, FIRB RBFR107AKG, FKZ 0325461
Funders: European Research Council, Italian Ministry of Education, University and Research, German Federal Ministry for Environment, Nature Conservation, and
Uncontrolled Keywords: Finite element method; Linear Elastic Fracture Mechanics; kerf-less technique; delamination; silicon; thin film solar cells
Subjects: Q Science > Q Science (General)
Research Area: Computer Science and Applications
Depositing User: Prof Marco Paggi
Date Deposited: 08 Oct 2015 07:55
Last Modified: 08 Oct 2015 08:03
URI: http://eprints.imtlucca.it/id/eprint/2761

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