Fabrication and evaluation of gallium-doped multicrystalline silicon wafers and solar cells - a promising material for future photovoltaics

Quality and stability of Ga-doped multicrystalline silicon (mc-Si) wafers and solar cells were intensively studied by quasi-steady-state photoconductance and microwave photoconductance decay lifetime measurements. Results show that as-grown Ga-doped mc-Si wafers have higher lifetimes if compared with B-doped wafers of the ingots grown by the same solidifying conditions. Further improvement up to 180 /spl mu/s was realized by phosphorus diffusion and hydrogen passivation at good lifetime regions. Simple screen printed solar cells made of both B-doped and Ga-doped wafers from top, center and bottom of the ingots showed the same tendency of conversion efficiency disregarding the different segregation coefficients of B and Ga in silicon. Carrier lifetimes of Ga-doped mc-Si wafers and solar cell characteristics found to be very stable under illumination. As a result, Ga-doped mc-Si wafers are promising material of a significant interest for future photovoltaics.