HIGH-EFFICIENCY SILICON SOLAR-CELLS BY RAPID THERMAL-PROCESSING

Silicon solar cell efficiencies of 16.9% have been achieved on 0.2 OME GA cm float zone silicon, using a simplified cost effective rapid ther mal process (RTP). Although the individual processing steps are not fu lly optimized yet, this represents the highest reported efficiency for solar cells processed with simultaneous front and back diffusion with no conventional high-temperature furnace steps. A diffusion temperatu re schedule coupled with an added short in situ slow cooling during RT P resulted in greater than 200 mum diffusion length and appropriate di ffusion profiles for high efficiency cells. Plasma enhanced chemical v apor deposition (PECVD) of SiN/SiO2 was used for surface passivation a nd antireflection coating. Conventional cells fabricated by furnace di ffusions and oxidations gave an efficiency of 18.8%. Process optimizat ion can further reduce the gap between the conventional and RTP/PECVD cells. (C) 1994 American Institute of Physics.