Hydrogen passivation of polycrystalline silicon solar cells by plasma deposition of silicon nitride

Abstract

Plasma-enhanced chemical vapor deposition (PECVD) is used for the deposition of a silicon nitride antireflection coating (ARC) onto 10*10 cm/sup 2/ Wacker Silso polycrystalline silicon solar cells. It is found that the short-circuit current I/sub sc/ is improved by 7 to 10% in comparison to reference cells with a standard screenprinted Ta/sub 2/O/sub 5/ coating. Part of the increase in I/sub sc/ is because of a smaller reflectivity of the silicon nitride ARC. The other part of the improvement comes from all enhanced average minority-carrier diffusion length (L/sub min/). The increase in L/sub min/ results from hydrogen passivation and is attributed to the generation of hydrogen ions during PECVD of Si/sub 3/N/sub 4/. It is shown that the passivation effect from PECVD of Si/sub 3/N/sub 4/ is comparable to that obtained with a 1/2 h hydrogen plasma treatment and that it is stable during a 1 h anneal at 700 degrees C. A significant influence of the substrate temperature during Si/sub 3/N/sub 4/ deposition in the range of 350 to 450 degrees C was not observed.<>