Influence of the pattern shape on the photonic efficiency of front-side periodically patterned ultrathin crystalline silicon solar cells

TL;DR

This study investigates how the shape of nanopatterns on ultrathin crystalline silicon solar cells affects their photonic efficiency, revealing optimal shapes and parameters for enhanced light absorption and current generation.

Contribution

It introduces a super-Gaussian mathematical model to analyze pattern shape effects and validates findings with experimental nanopatterned silicon slabs.

Findings

Optimal pattern shapes depend on silicon thickness

Cylindrical patterns are suboptimal compared to other shapes

Broad parameter zones reduce fabrication sensitivity

Abstract

Patterning the front side of an ultra-thin crystalline silicon (c Si) solar cell helps keeping the energy conversion efficiency high by compensating for the light absorption losses. A super-Gaussian mathematical expression was used in order to encompass a large variety of nanopattern shapes and to study their influence on the photonic performance. We prove that the enhancement in the maximum achievable photo-current is due to both impedance matching condition at short wavelengths and to the wave nature of light at longer wavelengths. We show that the optimal mathematical shape and parameters of the pattern depend on the c Si thickness. An optimal shape comes with a broad optimal parameter zone where fabricating errors would have much less influence on the efficiency. We prove that cylinders are not the best suited shape. To compare our model with a real slab, we fabricated a nanopatterned c Si slab via Nano Imprint Lithography.