Fracture strength of silicon solar wafers with different surface textures

Surface texturing is widely used in modern photovoltaic converters to improve light capture and increase efficiency. This paper focuses on the influence of the surface texture on the mechanical strength of silicon wafers. Various existing test methods and approaches for measuring the mechanical strength of silicon wafers are discussed and reviewed. The surface morphology of silicon wafers with different textures is characterized by scanning electron microscopy (SEM). The mechanical strength of thin (<200 μm) silicon wafers with different surface textures is measured with a ring-on-ring bending test. A finite element method (FEM) is used to calculate the maximum stress. Weibull statistical theory is applied to the measured fracture stresses. The mean fracture strength, its standard deviation, the Weibull characteristic strength, and the Weibull modulus are obtained for silicon wafers with various surface textures. The fracture strength of silicon wafers is strongly affected by the surface texture. It is found that the fracture strength of silicon wafers with pyramidal textures increases with decreasing size of the pyramids. A new type of surface texture produced by a V2O5 selective oxidation exhibited fracture comparable or higher than that of the wafers with conventional pyramidal textures produced by alkaline etching.