Influence of the boron emitter profile on V OC and J SC losses in fully ion implanted n‐type PERT solar cells

In this work, we report on fully ion implanted 156 × 156 mm 2 n‐type PERT solar cells fabricated in an industry‐capable process. The implant damage of phosphorous and boron was co‐annealed in a single furnace annealing step. The cells feature a screen‐printed front side metallization and an evaporated rear side metallization. The influence of boron emitter profile on the open‐circuit voltage V OC and the short‐circuit current density J SC was studied by comparing two boron doses (2.5 × 10 15  cm −2 , 3 × 10 15  cm −2 ) and two annealing durations (20 min, 80 min). The solar cells reach tightly distributed efficiencies above 20% (20.3% maximum). Cells featuring an emitter implanted with 2.5 × 10 15  cm −2 boron dose annealed for 80 min show the highest open‐circuit voltages up to 668 mV. As compared to implied open‐circuit voltages measured on non‐metallized cell precursors, this corresponds to a metallization‐induced voltage loss of 14 mV. For the shorter annealing time (corresponding to a shallower profile) but same boron dose, the V OC loss is 18 mV. The fact that the cells with the higher boron dose of 3 × 10 15  cm −2 showed lower V OC values indicates that the recombination at the Ag/Al‐p + Si contacts is not totally dominating. We determine the recombination current densities of the metallized emitter regions to 900–1900 fA cm −2 . Contrary to the dependence of V OC on the emitter profile, J SC is lower for deeper emitters. The loss in J SC is visible in the internal quantum efficiencies IQE at short wavelengths. Strategies for an optimization of both quantities, J SC and V OC , are discussed.