High Capacity Inline Annealing for High Efficiency Silicon Solar Cells

26th European Photovoltaic Solar Energy Conference and Exhibition; 1089-1093
Most high-efficiency concepts for silicon solar cells utilise passivated surfaces and/or novel metallisation approaches. For these devices an anneal step, preferential in forming gas ambient, is beneficial or even crucial. Annealing is known to activate or improve surface passivation, facilitate metal-silicide formation, improve adhesion of metal contacts and cure potential crystal damage. Challenges for industrial solutions of anneal processes are a precise control of the process atmosphere and temperature, as well as a high throughput and easy integration into production lines. We present a high capacity inline annealing system that addresses these tasks with a throughput of over 1000 wafers per hour. The gas locks, located at the entrance and exit of the furnace, allow for an effective separation of laboratory and forming gas process ambient, which results in a residual oxygen concentration of a few ppm. Inline annealed silicon solar cells with a thermal oxide passivated rear surface show the same conversion efficiency as reference cells, which are annealed in a single wafer reactor. The specific cost of inline annealing in forming gas is calculated to be below 1.1 €ct/Wp.