Influence of PECVD SiOx and SiNx:H films on optical and passivation properties of antireflective porous silicon coatings for silicon solar cells

The meso-porous silicon layer (PS) is a promising material to reduce the surface reflectance of solar cells. PS layers were grown on the front surface n(+) emitter of n(+)-p mono-crystalline Si junction. Single layers PS antireflection coating (ARC) achieved around 8% of effective reflectivity in the wavelength range between 400 to 1100 nm. To improve the stability and the passivation properties, and to reduce the reflectivity of PS ARC, the design of PECVD silicon oxide (SiOx) and silicon nitride (SiNx:H) layers were investigated. Optimised SiOx and SiNx layer deposited on PS decreased the effective reflectivity respectively to similar to 3.8% and similar to 7% between 400 and 1000 nm. Open circuit voltage (V-oc) measurements were carried out on all the samples by suns-V-oc method and showed an improvement of 20% of the surface passivation quality brought by the nitride layer after rapid thermal anneal (RTA). Using the experimental reflectivity results and taking into account the surface passivation quality of the samples, numerical simulations predict an enhancement of the photogenerated current exceeding 49% for the PS/SiOx stacks. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim