Influence of defect type on hydrogen passivation efficacy in multicrystalline silicon solar cells

We examine the effectiveness of hydrogen passivation as a function of defect type and microstructure at grain boundaries (GBs) in multicrystalline silicon. We analyze a solar cell with alternating mm‐wide bare and SiNx‐coated stripes using laser‐beam‐induced current, electron backscatter diffraction, X‐ray fluorescence microscopy, and defect etching to correlate pre‐ and post‐hydrogenation recombination activity with GB character, density of iron‐silicide nanoprecipitates, and dislocations. A strong correlation was found between GB recombination activity and the nature/density of etch pits along the boundaries, while iron silicide precipitates above detection limits were found to play a less significant role. Copyright © 2010 John Wiley & Sons, Ltd. Studies on a specially prepared mc‐Si solar cell indicate that the recombination activity at some grain boundaries reduces significantly upon hydrogen passivation, whereas at other ones do not. Our detailed analytical investigations demonstrate that defect microstructure plays a dominant role in determining passivation efficacy. The density of countable etch pits along a grain boundary is found to be the principal property governing post‐passivation recombination activity, while Fe‐rich precipitate decoration was found to play a less significant role.