Simulation of mechanical stress during bending tests for crystalline wafers

The mechanical stability of wafers is one of the major keys to establish the next generation of thinner and larger crystalline silicon solar cells. Therefore, it is necessary to have facilities for the testing of wafer stability. In all those tests the force and the displacement of the force punch are controlled. But, the interesting values are the stresses in the wafer's plane. As these stresses can not be measured during the tests, simulations of various test scenarios are performed. In this paper we show the necessity of knowing the stress distributions induced by the bending facilities, we give examples for some often used test geometries and assess them with regard to the possibilities to study different characteristics of wafers. Our results are necessary to interpret the experimental data from any kind of bending test facilities.