High efficiency polycrystalline silicon solar cells by continuous plasma deposition and laser recrystallization

Solar cells of up to 12% efficiency have been fabricated on laser recrystallized fine grain polycrystalline silicon films produced by high pressure plasma (hpp) aided hydrogen reduction of trichlorosilane. The hpp system was operated in a continual mode to produce microcrystalline silicon films continually using finite size temporary molybdenum substrates. The major improvement over previous devices of this type is in the elimination of oxygen contamination during laser recrystallization. This resulted in a reduction in the dark excess junction current and improvement in minority carrier diffusion length. The devices are found to be diffusion limited, with diffusion current coefficients in the range of 3 × 10^-12to 5 × 10^-12A/cm²when the base resistivity was 0.4 to 0.5 Ω-cm p-type.