Towards 20% efficient large‐area screen‐printed rear‐passivated silicon solar cells

Abstract

We have implemented a baseline solar cell process based on today's standard industrially manufactured silicon solar cells. Using this process, we achieve conversion efficiencies up to 18.5% applying 125 Â 125 mm² pseudo-square p-type 2-3 Ω cm boron-doped Czochralski silicon wafers featuring screen-printed front and rear contacts and a homogenously doped 70 Ω/□ n + -emitter. Optimizing a print-on-print process for the silver front side metallization, we reduce the finger width from 110 to 70 mm, 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 S eff,rear = 350 cm/s for a full-area Al back surface field down to S eff,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 short-circuit current density J sc up to 38.9 mA/cm² and the open-circuit voltage V oc up to 662 mV. The detailed solar cell analysis reveals potential to further increase the conversion efficiency towards 20% in the near future.

21.2%-efficient fineline-printed PERC solar cell with 5 busbar front grid

“…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. cess flow is described in detail in [6]. Here we just highlight the most important process steps.…”

D-M-D Plasmonic Anti-Reflector for Next-Generation Thin c-Si Solar Cell Applications

“…There are many dielectrics which can be potential candidate for rear surface passivation such as aluminum oxide (Al 2 O 3 ) [23], thermally grown silicon oxide (SiO 2 ) [24], silicon nitride (SiN x ) [25,26], amorphous silicon (a-Si) [27], silicon carbide (SiC) [19], silicon oxynitride (SiON) [28], etc. Recently, SiO x /SiN x stack used for passivation has been reported to give below 10 cm/s effective recombination velocity [29].…”

Impurity-related limitations of next-generation industrial silicon solar cells

“…1(a), a phosphorus-diffused 80 Ω/sq n + emitter is assumed, which is passivated with fired SiN x . The metal fingers have a distance of 2 mm and are 70 μm wide, a typical finger width reached by advanced screen printing or stencil techniques [7]. The cell front can be characterized as advanced realistic industrial standard.…”