Process simplifications in large area hybrid silicon heterojunction solar cells

• We report progress in the development of hybrid SHJ cells with Ni/Cu front contacts.
• Various rear contact layers are tested as alternative to the commonly used ITO/Ag.
• The impact of low temperature contact annealing on ITO properties is studied.
• We show that NiSix formation can be skipped without compromising adhesion quality.
• 21.1% efficient cells are presented and results are compared to state-of-the-art n-PERT cells.

Recently, large area hybrid silicon heterojunction cells (SHJ) with nickel/copper (Ni/Cu) plated front contacts were shown to benefit from a simpler processing sequence than n-PERT cells featuring a boron diffused rear emitter. Hybrid refers here to the combination of a diffused front surface field (FSF) and a SHJ rear emitter. In this work, further process simplifications for such hybrid SHJ cells are evaluated. Based on reflectance and adhesion considerations, stacks of tin-doped indium oxide and copper (ITO/Cu) and chromium/silver (Cr/Ag) are tested as alternative to the previously chosen ITO/Ag rear contact stack. Using ITO/Cu/Al as rear contact stack, average efficiencies of 20.8±0.2% are presented on 6-inch wafers. We also demonstrate that the excimer laser annealing step previously employed to form nickel silicides at the front side can be skipped without comprising solder tab adhesion quality.