Series resistance in polysilicon contacted solar cells

Series resistance values between 0.2 and 0.43 Ω cm² have been obtained in solar cells contacted with polysilicon in 2.6% of the area. These values include the resistance of the polysilicon-single crystal silicon interface. Various size devices were fabricated in 4" wafers, and a VLSI polysilicon emitter technology was applied to fabricate polysilicon contacts to the emitter front surface. The polysilicon-silicon interface was produced using either an HF etch or RCA clean before polysilicon deposition and half of the wafers were implanted with fluorine to assess the passivating effects on the polysilicon-silicon interface. The drive-in time of the impurities from the polysilicon into the silicon was also varied. The main results are that the series resistance is lower in all fluorinated samples, either HF or RCA. The series resistance decreased monotonically in the HF devices as the drive-in time increased from 20\´ to 80\´ whereas little change is seen in RCA devices