Application of new doping techniques to solar cells for low temperature fabrication

摘要

New techniques to fabricate highly doped p-type and n-type crystalline-Si (c-Si) layers at relatively low temperature were applied to solar cell devices. A very thin n-type emitter is formed by exposing phosphine (PH3) gas on c-Si surface around 600 °C. PH3 molecules can react with dangling bonds on the surface, and incorporate into shallow region in c-Si bulk. This thin doped layer is expected to decrease recombination near the surface. Another technique is aluminum induced crystallization to fabricate highly doped p-type c-Si layer which can dissolve Al atom up to the solubility limit. In this method, poly-crystalline Si of more than 100 μm grain size can be obtained around 500 °C. We applied these techniques to form pn-junction or back surface field of c-Si solar cells to reduce carrier recombination on c-Si surface and the parasitic optical absorption of these doped layers.