19.4% -Efficient Large Area Rear-Passivated Screen-Printed Silicon Solar Cells

Abstract

We have implemented a baseline solar cell process based on today’s standard industrially manufactured silicon solar cells with conversion efficiencies up to 18.5% applying 125×125 mm2 2-3 Ωcm borondoped Cz silicon wafers, screen-printed front and rear contacts, and a homogenously doped 70 /sq n-emitter. Optimizing a print-on-print process, we reduce the silver finger width from 110 μm to 70 μm which increases the conversion efficiency up to 18.9% due to the reduced shadowing loss. In order to further increase the efficiency, we implement two different dielectric rear surface passivation stacks: (i) a silicon dioxide/silicon nitride stack and (ii) an aluminium oxide/silicon nitride stack. The rear contacts to the silicon base are formed by local laser ablation of the passivation stack and aluminium screen printing. The dielectric layer stacks at the rear decrease the surface recombination velocity from Seff,rear = 350 cm/s for a full-area Al-BSF down to Seff,rear = 70 cm/s and increase the internal reflectance from 61% up to 91%. The improved solar cell rear increases the conversion efficiency  up to an independently confirmed value of 19.4%. The detailed solar cell analysis reveals potential to further increase the conversion efficiency towards 20% in the near future.