Tailoring the degradation of the quantum efficiency of multicrystalline silicon solar cells caused by non-optimized heavy phosphorus diffusion

The effect of heavy phosphorus diffusion on the quality of multicrystalline silicon is investigated by studying the quantum yields measured with and without bias light for solar cells fabricated on Polix (Photowatt) and Eurosolare material. A serious degradation is observed in the quantum yield of cells in which heavy P diffusion is performed at 950°C, suggesting that the surface region extending deep beyond the n⁺⁺ P-diffused layer is seriously damaged. There are no signs of substantial degradation when the heavy P diffusion is performed at 900°C or after a thermal treatment at 950°C in the absence of P diffusion