Efficiency Limitations of Multicrystalline Silicon Solar Cells Due to Defect Clusters

Multicrystalline Si wafers used in commercial solar cell fabrication exhibit a tendency to form large “clusters” of defects, which remain laterally separated from each other. Defect clusters are also sites of impurity precipitation. Because precipitated impurities cannot be gettered by the conventional processes used in Si solar cell fabrication, defect clusters constitute low-performing regions in the cell. They shunt the device and constitute the primary efficiency limiting mechanism in current solar cells. We show that the efficiency loss caused by defect clusters can exceed 3–4 absolute points.