Solar cells with annealed amorphous Si/sub 0,8/C/sub 0,2//Si heterojunction and a-SiC/sub x/:H backsurface passivation

This paper presents further optimization steps of a fabrication process for solar cells with an emitter consisting of an annealed n-type Si/sub 0,8/C/sub 0,2//p-type c-Si heterojunction. We show that emitters produced in this way can have an emitter saturation current density as low as 0.1 pAcm/sup -2/. The emitter then will limit the open circuit voltage of a solar cell to about 690 mV at 1 sun illumination. However, to reach this limit, recombination within the bulk and at the solar cell backside must be strongly reduced. We present solar cell results applying a backsurface passivation scheme using phosphorus doped amorphous silicon carbide films. The dependency of passivation properties of these films on wafer doping density is studied. To control the quality of the emitter and the backsurface passivation we measure the effective lifetime of minority carriers in wafers using the contactless quasi steady-state photoconductance decay technique.