TY - JOUR

T1 - Numerical modelling and validation of thermally-induced spalling

AU - Berardone, Irene

AU - Kajari-Schröder, Sarah

AU - Niepelt, Raphael

AU - Hensen, Jan

AU - Steckenreiter, Verena

AU - Paggi, Marco

N1 - Funding Information: Marco Paggi would like to acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 306622 (ERC Starting Grant “Multi-field and multi-scale Computational Approach to Design and Durability of PhotoVoltaic Modules”-CA2PVM). Irene Berardone acknowledges the support of the Italian Ministry of Education, University and Research to the Project FIRB 2010 Future in Research “Structural mechanics models for renewable energy applications” (RBFR107AKG). This work was also supported by the Federal Ministry for Environment, Nature Conservation, and Nuclear Safety under the contract FKZ 0325461 and by the state of Lower Saxony, Germany.

PY - 2015/8

Y1 - 2015/8

N2 - 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.

AB - 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.

KW - delamination

KW - Finite element method

KW - kerf-less technique

KW - Linear Elastic Fracture Mechanics

KW - silicon

KW - thin film solar cells

UR - http://www.scopus.com/inward/record.url?scp=84948417396&partnerID=8YFLogxK

U2 - 10.1016/j.egypro.2015.07.121

DO - 10.1016/j.egypro.2015.07.121

M3 - Conference article

AN - SCOPUS:84948417396

VL - 77

SP - 855

EP - 862

JO - Energy Procedia

JF - Energy Procedia

SN - 1876-6102

T2 - 5th International Conference on Silicon Photovoltaics, SiliconPV 2015

Y2 - 25 March 2015 through 27 March 2015

ER -