Formation of High-Quality Passivation Films for Solar Cells by Cat-CVD

Abstract

Back-contact c-Si solar cells can realize superior performance due to no shadowing loss. Surface passivation with excellent quality is required for achieving sufficient conversion efficiency in the back-contact cells. Cat-CVD can produce high-quality passivation films owing to its plasma-damage-less nature. SiN_x deposition at a low temperature and successive post annealing leads to a surface recombination velocity (SRV) of < 5 cm/s. The exposure of c-Si wafers to catalytically generated phosphorus radicals can form ultra-thin highly-doped layers (Cat-doping). This P-doped region acts to reduce an SRV to < 2 cm/s by combining with a Cat-CVD SiN_x film. We have also established the passivation of rear c-Si surfaces by Cat-CVD a-Si with suppressing epitaxial growth by introducing ultra-thin oxide layers formed by dipping in H₂O₂. The formation of doped a-Si by Cat-doping has also been demonstrated, which will be applicable to the formation of patterned doping regions in Si heterojunction back-contact cells.