Efficient silicon heterojunction solar cells based on p- and n-type substrates processed at temperatures <220°C

We present the optimization and characterization of heterojunction solar cells consisting of an amorphous silicon emitter, a single crystalline absorber and an amorphous silicon rear side which causes the formation of a back surface field (a-Si:H/c-Si/a-Si:H). The solar cells were processed at temperatures < 220 degrees C. An optimum of the gas phase doping concentration of the a-Si:H layers was found. For high gas phase doping concentrations, recombination via defects located at or nearby the interface leads to a decrease in solar cell efficiency. We achieved efficiencies > 17% 17% on p-type c-Si absorbers and > 17.5% on n-type absorbers. In contrast to the approach of Sanyo, no additional intrinsic a-Si:H layers between the substrate and the doped a-Si:H layers were inserted. Copyright (C) 2006 John Wiley & Sons, Ltd.