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The HIP-MWT+ solar cell concept on N-type silicon and metallization-induced voltage losses
We present high-performance metal wrap through+ (n-HIP-MWT+) solar cells (239 cm² area) on n-type Czochralski-grown silicon (Cz-Si) wafers with a boron-doped front-side emitter. Peak conversion efficiencies of = 19.5 % are measured using a black chuck. Short-circuit current density jSC, open-circuit voltage VOC, and fill factor FF are 39.6 mA/cm², 650 mV, and 75.7 %, respectively. The loss in VOC, caused by front and rear side metallization, is found to be 16 mV for the n-HIP-MWT+ as well as for H-pattern cells with electrically non-contacting busbars fabricated in parallel, whereas the use of electrically contacting busbars in case of the H-pattern cells leads to a significantly higher VOC loss of 24 mV. The saturation current density underneath the front silver-aluminum (Ag-Al) contacts is determined to be j0,met,Ag-Al ≈ 3500 fA/cm², which is three times larger than j0,met,Ag found for the silver contacts on the rear side. The high j0,met,Ag-Al values are assumed to originate from deep spikes formed during Ag-Al paste contact firing. This assumption is supported by numerical simulations performed with Sentaurus Device.