Shedding light on Solar Cells
The competitiveness of solar cell technology in energy production is strongly dependent on its price. Rapid thermal processing (RTP) directly addresses the issue of fabrication costs by reducing the processing time in comparison with conventional furnace processing. In this way, the throughput is improved while high cell efficiency is maintained. However, there are some major concerns related to wide industrial applications of RTP in solar cell production. The FLASH project aimed at developing an industrial RTP system adapted to Photovoltaic cell production that will be applicable to all main thermal steps in the fabrication of solar cells. Towards this objective the FLASH research group, had a systematic view on the influence of UV radiation on the diffusion process in silicon in the wafer surface. The fundamental investigation has been executed in a prototype reactor equipped with additional excimer lamps that allow the switching on of these UV lamps independently from the conventional lamps. The comparison between samples that were processed with additional UV light and those processed with the normal spectrum of the RTP lamps was performed for identical processing temperatures. The excimer UV lamps were located above the wafer and emitted at a wavelength and with a power density sufficient to observe UV-enhanced diffusion, as claimed in relevant publications. However this UV-enhanced diffusion did not occur, indicating that other diffusion mechanisms must be explored.
