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Issue 19, 2017
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Photoelectrochemical water reduction over wide gap (Ag,Cu)(In,Ga)S2 thin film photocathodes

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Abstract

The effects of partial replacement of Cu with Ag in a Cu(In,Ga)S2 (CIGS) thin film on its structural, optical, electrostructural, and photoelectrochemical (PEC) properties were investigated, in order to improve its performance for PEC water reduction under sunlight illumination. Results from X-ray diffraction (XRD) analyses revealed the successful partial replacement of Cu with Ag to form solid-solutions with different Ag/(Ag + Cu) ratios (A(x)CIGS, x = Ag/(Ag + Cu) = 0.1, 0.2, 0.3 and 0.4), as confirmed by a gradual change in the (112) reflections to smaller 2θ angles with increasing Ag/(Ag + Cu) ratio. Analyses of the photoabsorption properties of the materials using photoacoustic spectroscopy indicated changes in the band gap energies associated with increasing the Ag/(Ag + Cu) ratio. In addition, valence band maximum potentials of A(x)CIGS were deepened gradually with increasing Ag/(Ag + Cu) ratio. After modifying these A(x)CIGS films with a CdS ultrathin (ca. 70 nm) layer and a Pt catalyst, the PEC water reduction properties were evaluated in an electrolyte solution with the pH adjusted to 6.5, under simulated sunlight (AM 1.5G) radiation. Compared to the CdS- and Pt-modified Ag-free A(x)CIGS (A(0)CIGS) films, appreciable enhancements in the PEC properties were observed for electrodes based on A(x)CIGS (x > 0) films, and the best PEC performance was obtained for the electrode based on the A(0.2)CIGS film. However, the electrode derived from the A(x)CIGS film with Ag/(Ag + Cu) ratios higher than 0.3 showed diminished PEC properties due to the partial conversion of its semiconducting properties from p-type to n-type.

Graphical abstract: Photoelectrochemical water reduction over wide gap (Ag,Cu)(In,Ga)S2 thin film photocathodes

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Publication details

The article was received on 02 Mar 2017, accepted on 15 Apr 2017 and first published on 19 Apr 2017


Article type: Paper
DOI: 10.1039/C7CP01348E
Citation: Phys. Chem. Chem. Phys., 2017,19, 12502-12508
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    Photoelectrochemical water reduction over wide gap (Ag,Cu)(In,Ga)S2 thin film photocathodes

    W. Septina, M. Sugimoto, D. Chao, Q. Shen, S. Nakatsuka, Y. Nose, T. Harada and S. Ikeda, Phys. Chem. Chem. Phys., 2017, 19, 12502
    DOI: 10.1039/C7CP01348E

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