Optimization of a firing furnace
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Olaisen, Birger Retterstøl
Scientist
This paper presents work on optimizing an RTC LA-309 firing furnace with four heat zones and water cooling. The belt speed and temperature setpoints in the different heat zones were used to vary the firing temperature profile, while air and water flows were held constant. It was found that the best results were achieved at a belt speed of 250 cm/min with a peak temperature on the wafer between 785°C and 830°C, and a time above 620°C between 11.6 seconds and 12.7 seconds. Solar cells of up to 15.5% efficiency and a fill factor up to 78% were fired at these parameters. Low temperatures combined with high belt speeds were found to give incomplete firing, while high temperature and slow belt speed gave high contact resistance at the interface between silicon and the contacts.
