Users watch growth of defects in silicon

The ESRF’s ID19 and BM05 beamlines have enabled scientists to watch the growth of carbon- based defects in silicon. The results could help in the development of silicon photovoltaics that are less affected by carbon impurities. Carbon is a common impurity in photovoltaic silicon, entering the crystal as carbon monoxide, which is formed by the contact of oxygen with neighbouring graphite components in industrial furnaces. Once inside, it can make the silicon harder to cut into ingots for wafer preparation, and initiates several types of crystal defects, which impact on both electrical and mechanical performance once the wafers are made into solar cells, reducing photovoltaic efficiency.According to researchers at the CNRS Institute of Materials Microelectronics and Nanosciences of Provence (IM2NP), and Aix- Marseille Université, both in France, “post mortems” of silicon ingots reveal little about how these defects develop