CoS Nanoflakes on Textured Silicon Coupled with Antimony-Decorated Tungsten Oxide for Efficient Liquid Junction Solar Cells

A unique liquid junction solar cell (LJSC) based on p-type hole-transporting CoS nanoflakes tethered to n-type textured silicon (T-Si) with pyramidal structures as photoanodes has been fabricated. A ferrocene/ferrocenium (Fc/Fc+) redox couple electrolyte and an electrocatalytic counter electrode film (CE) of antimony nanostructures anchored to tungsten oxide (SbNSs/WO3) are used in the cell. The cell delivers a power conversion efficiency (PCE) of ∼8.4%, which is superior by ∼97% to the LJSCs without CoS and SbNSs. CoS nanoflakes function as independent photosensitizers, generate electron/hole pairs, and increase photocurrents. They also facilitate photo-generated hole transport from T-Si to Fc and suppress charge recombination, leading to an improvement in PCE by ∼82% compared to pristine T-Si. Simultaneously, the composite of SbNSs/WO3 outperforms both SbNSs and WO3 due to better electrocatalytic activity and low overpotential for Fc+ reduction at the CE/Fc+ interface. The CoS/T-Si/Fc/Fc+/SbNSs/WO3 LJSC architecture results in a stable, reproducible performance wherein exposure to extended illumination results in a moderate loss in the PCE, indicating that this strategy of using CoS and Sb can be applied to other hybrid or tandem silicon-based solar cells.