We evaluate industrial-type PERC solar cells applying a 5 busbar front grid and fineline-printed Ag fingers. We obtain finger widths down to 46 μm with stencil printing. This compares to finger widths of 62 μm to 66 μm when applying print-on-print. The 5 busbar front grid (2.5 mm total busbar width) with the best dual print process reduces the shadowing loss of the front grid to 4.0% compared to 5.8% for a conventional 3 busbar (3.9 mm total busbar width) front grid printed with print-on-print. The 1.8% reduction in shadowing loss result in equal parts from the reduced finger width with stencil print as well as from a reduced total busbar width of the 5 busbar design. The resulting PERC solar cells with 5 busbars demonstrate independently confirmed conversion efficiencies of 21.2% compared to 20.6% efficiency of the 3 busbar PERC solar cell. The increased conversion efficiency is primarily due to an increased short circuit current resulting from the reduced shadowing loss. The experimental results agree well with an analytical model for the front grid related efficiency losses. To our knowledge, 21.2% conversion efficiency is the highest value reported so far for industry typical silicon solar cells with printed metal front and rear contacts.
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Dullweber et al. (2014) studied this question.