We report the fabrication of p-type silicon (Si) photocathodes consisting of well-ordered Si microwire (Si-MW) arrays coupled with non-precious and earth-abundant amorphous oxygen-rich molybdenum oxysulfide (MoO x S y ) as both a hydrogen evolution catalyst and a passivation layer. The MoO x S y is conformally grown on the Si-MW surface through photo-assisted cyclic voltammetric (CV) deposition. By adjusting the cycle numbers of the CV deposition, Si-MW array electrodes with different MoO x S y catalyst loadings (Si-MWs@MoO x S y ) have been obtained and comprehensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Xray photoelectron spectroscopy (XPS), and Raman and Fourier-transform infrared spectroscopies. The photoelectrochemical performance of the Si-MWs@MoO x S y cathodes toward water reduction is investigated and compared with that of platinum nanoparticle decorated Si-MW array electrodes (Si-MWs@PtNPs). An optimized Si-MWs@MoO x S y photocathode is found to exhibit activity comparable to that of the Si-MWs@PtNPs one, with a much better stability in acidic medium. In neutral electrolyte, Si-MWs@MoO x S y outperforms Si-MWs@PtNPs in terms of both activity and stability. Given the low materials cost, easy and well-established electrode fabrication procedure, and high 1 3 5 7 Please cite this article as: X.-Q. Bao, et al., Amorphous oxygen-rich molybdenum oxysulfide Decorated p-type silicon microwire Arrays for efficient photoelectrochemical water reduction, Nano Energy (2015), http://dx.doi.org/10.1016/j.nanoen.2015.06.014demonstrated photoelectrochemical performance, the Si-MWs@MoO x S y arrays reported here hold substantial promise for use as low-cost and efficient photocathodes for water reduction.

Herein, it is demonstrated, by using industrial techniques, that a passivation layer with nanocontacts based on silicon oxide (SiOx) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se2 (CIGS) solar cells. Two approaches are applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 and 500 °C, the SiOx passivation layer demonstrates positive passivation properties, which are supported by electrical simulations. Such positive effects lead to an increase in the light to power conversion efficiency value of 2.6% (absolute value) for passivated devices compared with a nonpassivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade‐off between passivation effect and charge extraction, as demonstrated by the trade‐off between open‐circuit voltage (Voc) and short‐circuit current density (Jsc) compared with fill factor (FF). For the first time, a fully industrial upscalable process combining SiOx as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results toward high‐performance and low‐cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12%, demonstrating the potential of SiOx as a passivation material for energy conversion devices.

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The influence of structural parameters of highly-ordered silicon nanowire arrays on their solar-driven HER performance is systematically investigated.