Performance Limitations of mc-Si Solar Cells Caused by Defect Clusters

Abstract

Multicrystalline silicon wafers used for solar cells exhibit defect clusters-localized crystal defects in and near grains of some specific orientations. Defect clusters are also dominant sites for impurity precipitation, and they remain ungettered and unpassivated through the solar cell processing. This paper describes characteristics of defect clusters, and shows, through theory and experiment, that defect clusters typically lower cell efficiency by 3 to 4 absolute percentage points. To recover this efficiency loss, it is necessary to getter precipitated impurities.