Lifetime improvements of multicrystalline silicon analysed by spatially resolved lifetime measurements

We investigated the gettering and passivation qualities of different industrial type processes for multicrystalline silicon solar cells. For gettering different phosphorus diffusion techniques forming the emitter including single and double side doping were realised. Additional hydrogen passivation by firing of a SiN:H-layer was performed. Processed wafers have been analysed by spatially resolved lifetime measurements. It is shown that the impact of phosphorus diffusion is most obvious in areas with small lifetimes. For these areas of poor quality the comparison between the different emitter formation showed best improvements for bifacial diffusion. The hydrogen passivation effect is more distinct from a double sided SiN:H-layer than from a single sided one. In comparison to the gettering effect of the phosphorus diffusion and phosphorus aluminium co-diffusion the bulk passivation effect from the SiN:H-layers are less effective in areas of poor material quality.