Faster and cheaper production of solar cells
The high cost of producing solar cells has meant that energy production from fossil fuels still remains a cheaper alternative. However, scientists have recently discovered that Rapid Thermal Processing (RTP) can significantly reduce solar cell production time and hence costs. As opposed to a conventional furnace, an RTP reactor uses light to heat the silicon wafers. What remains to be seen is whether or not RTP can be effectively implemented on an industrial scale. Qualiflow-JIPELEC collaborated with three German partners in order to realise this goal. Their approach consisted of defining requirements followed by the design and construction of a relevant prototype. An important step was in establishing the limits of the component processes of RTP: Rapid Thermal Firing (RTF), Rapid Thermal Diffusion (RTD) and Rapid Thermal Oxidation (RTO). The challenge with RTP is to cut production time without compromising the efficiency of the resulting solar cells. The time constraints on RTD meant that the reactor temperature had to be increased substantially, up to 950 degrees Celsius. This high temperature negatively impacts the production of multicrystalline but does not affect mono-crystalline wafers. It was not possible to demonstrate any distinct advantages of RTD. A similar discovery was made with respect to the RTO, such that it can be used with mono-crystalline materials but not with multicrystalline or EFG silicon. However, in contrast to RTD, small but important gains in efficiency were observed in Cz-Si wafers prepared with RTO. Further research is necessary before solar cells can be mass-produced with RTP techniques, though Qualiflow-JIPELEC's work represents an important first step in this direction.
