Synchrotron X-ray Micro-diffraction – Probing Stress State in Encapsulated Thin Silicon Solar Cells

There has been a strong commercial push towards thinner silicon in the solar photovoltaic (PV) technologies due to the significant cost reduction associated with it. However, in current products made from crystalline solar cell technologies, normal in-plane tensile stress resulting in fracture of silicon cells are observed. To further understand this phenomenon, the synchrotron X-ray micro-diffraction tool was used to perform stress measurements and mapping of the solar cells in the vicinity of the most typically observed crack initiation location, the solder joint. This technique is unique as it has the capabilities to quantitatively determine the stresses and map these stresses with a micron resolution, all while the silicon cells are in encapsulation. A fundamental understanding of the stress magnitudes as well as microstructural characteristics that could lead to crack initiation and propagation could be obtained with this technique. This also confirms that the control of mechanical stress is the key to enable thin silicon solar cell technologies in the coming years.