Comparison of different rear contacting approaches for industrial PERC solar cells on MC-SI wafer
The technology transfer of highly efficient solar cell concepts (i.e. passivated emitter and rear cell PERC) to industry can help reduce their production cost. This work appraises three different industrial approaches for the technology transfer and a conventional processing with a fair comparison. A significant improvement compared to conventional processing was obtained. All advanced approaches lead to an increase in open circuit voltage and short circuit current. This testifies to the benefits of improved passivation of the rear surface and a bettered light trapping. The optimal processing window for the advanced approaches has lower fill factor than the conventional processing. However, the reduction does not result in lower conversion potential. Finally, the PERC type devices deliver a significant increase of more than 0.4 % absolute in conversion efficiency. The structure which proved best was based on laser fired contacts (LFC). A maximum efficiency of 17.0 % has been achieved on 1.8 ohm cm multi-crystalline silicon.