Ribbons Affect Movement of Cracked Solar Cells

Cracking of crystalline silicon photovoltaic cells remains a challenging topic in accurately assessing the long-term reliability and performance of affected modules. Cells can be damaged in every stage throughout the lifetime of a photovoltaic module, ranging from manufacturing, transportation, and installation to operation. Initially, the metallization can be able to bridge the gap of fractured cells and keep individual cell fragments electrically connected. However, photovoltaic modules and cells experience thermo-mechanical stresses during operation from temperature changes and pressure cycles of wind and snow loads. This causes the cell fragments to move, which, in turn, can lead to the wear out of the metallization and, consequently, to power loss or a safety hazard. The rate at which this degradation mechanism proceeds is currently unknown. Hence, in this work, we quantify the cell fragment movement of polycrystalline and monocrystalline mini-modules. By using digital image correlation, we were able to extract the normal crack opening and tangential sliding distances of adjacent cell fragments during heating of the mini-modules. Those distances are essential to develop wear-out models for the metallization and determine the rate of the degradation mechanism. We found that the interconnect technology has a significant impact on the direction and quantity of the cell fragment movements.