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Electrochemical Self-Assembly of Nanostructured CuSCN/Rhodamine B Hybrid Thin Film and Its Dye-Sensitized Photocathodic Properties.

Iwamoto T, Ogawa Y, Sun L, White MS, Glowacki ED, Scharber MC, Sariciftci NS, Manseki K, Sugiura T, Yoshida T - J Phys Chem C Nanomater Interfaces (2014)

Bottom Line: High loading of RB into the film has been achieved to reach a CuSCN:RB volume ratio of approximately 2:1.The crystallographic orientation of the nanostructure with respect to the substrate can be controlled.Photoelectrochemical study on the porous crystalline CuSCN obtained after the DMA treatment and sensitized with RB revealed sensitized photocathodic action under visible light illumination, indicating the potential usefulness of the porous CuSCN electrodes for construction of tandem dye-sensitized solar cells.

View Article: PubMed Central - PubMed

Affiliation: Center of Innovative Photovoltaic Systems (CIPS), Gifu University , Yanagido 1-1, Gifu, Gifu 501-1193, Japan.

ABSTRACT
Nanostructured hybrid thin films of CuSCN and rhodamine B (RB) are electrochemically self-assembled (ESA) by cathodic electrolysis in an ethanol/water mixture containing Cu(2+), SCN(-), and RB. By selecting the solvent, Cu(2+)/SCN(-) ratio, and the concentration of RB, we demonstrate several control parameters in the film formation. High loading of RB into the film has been achieved to reach a CuSCN:RB volume ratio of approximately 2:1. The RB solid could almost completely be extracted from the hybrid film by soaking the film in dimethylacetamide (DMA), leading to a large increase of the surface area. The crystallographic orientation of the nanostructure with respect to the substrate can be controlled. Efficient quenching of fluorescence of RB has been observed for the CuSCN/RB hybrid film, implying hole injection from RB excited state to CuSCN. Photoelectrochemical study on the porous crystalline CuSCN obtained after the DMA treatment and sensitized with RB revealed sensitized photocathodic action under visible light illumination, indicating the potential usefulness of the porous CuSCN electrodes for construction of tandem dye-sensitized solar cells.

No MeSH data available.


I–V curves measured atbulk CuSCN (a) electrodeposited without RB and porous crystallineCuSCN (b) electrodeposited with 1.0 mM RB and RB subsequently removedby DMA treatment, measured in the dark (hashed lines) and under illumination(solid lines) with visible light (100 mW cm–2) generated by a 500 W Xe lamp equipped with UV and IR cutoff filters.The CuSCN films were sensitized by readsorbing RB by soaking in a0.5 mM RB aqueous solution for 1 h. The electrolyte was a deaeratedaqueous solution of 0.1 M methylviologen chloride.
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fig10: I–V curves measured atbulk CuSCN (a) electrodeposited without RB and porous crystallineCuSCN (b) electrodeposited with 1.0 mM RB and RB subsequently removedby DMA treatment, measured in the dark (hashed lines) and under illumination(solid lines) with visible light (100 mW cm–2) generated by a 500 W Xe lamp equipped with UV and IR cutoff filters.The CuSCN films were sensitized by readsorbing RB by soaking in a0.5 mM RB aqueous solution for 1 h. The electrolyte was a deaeratedaqueous solution of 0.1 M methylviologen chloride.

Mentions: We carried out photoelectrochemicalmeasurements on RB-sensitizedporous CuSCN electrodes. The electrodes were the pure CuSCN with arelatively high surface area, that electrodeposited from Cu2+ rich bath without RB, and a highly porous CuSCN made by electrodepositionfrom a SCN– rich bath containing 1.0 mM RB whichthen was removed by the DMA treatment. These electrodes were soakedin an aqueous solution of RB for sensitization. Thus, we prepareda dye-sensitized photocathode with the RB dye shown to undergo photoinducedhole transfer. However, the lack of a suitable redox electrolyte isa significant problem for studying photocathodic sensitization ofCuSCN.5,17 Iodide/triiodide redox electrolyte typicallyused in DSSCs reacts with CuSCN to convert it to CuI that dissolvesrather well in many polar organic solvents. Adsorption of RB moleculesto CuSCN was unfortunately not so stable, as recognized by the factthat the electrolyte solution was clearly colored by desorbed RB bothfor organic and aqueous solutions. For this reason, it was not usefulto use Co complex redox systems, which are kinetically highly reversible,because fast recombination from the uncovered surface of CuSCN orexposed FTO actually killed the voltage under illumination. Stablyadsorbed highly rectifying dyes are needed for effective use of Coredox,6 which are missing at this stage.Thus, we have employed an aqueous solution of methylviologen chlorideas the electron acceptor. The electrode was reasonably stable in thiselectrolyte and exhibited a clear photocathodic action under visiblelight illumination as shown in Figure 10. PureCuSCN film sensitized with RB exhibits about 0.2 V photocurrent onsetvoltage and 22 μA cm–2 photocathodic current;these values increased to ca. 0.3 V and 32 μA cm–2 for the porous CuSCN electrode prepared by hybrid electrodepositionwith RB, extraction of RB, and readsorption of RB. Clearly, enlargedsurface area made the color of the film more intense than that ofthe pure CuSCN, obviously contributing to the increased current. Poorlyrectified dark current for pure CuSCN (Figure 10a) can be associated with the the bare FTO surface being in contactwith the electrolyte, allowing direct charge transfer to methylviologen. Because theporous crystalline CuSCN (Figure 10b) coversthe FTO better than pure CuSCN, the dark current is well-rectifiedand higher voltage is achieved. Despite efforts to find a stable dye–electrolytesolution combination, the RB dye still desorbs from the surface duringmeasurement, likely contributing to the unusually low photocurrent.


Electrochemical Self-Assembly of Nanostructured CuSCN/Rhodamine B Hybrid Thin Film and Its Dye-Sensitized Photocathodic Properties.

Iwamoto T, Ogawa Y, Sun L, White MS, Glowacki ED, Scharber MC, Sariciftci NS, Manseki K, Sugiura T, Yoshida T - J Phys Chem C Nanomater Interfaces (2014)

I–V curves measured atbulk CuSCN (a) electrodeposited without RB and porous crystallineCuSCN (b) electrodeposited with 1.0 mM RB and RB subsequently removedby DMA treatment, measured in the dark (hashed lines) and under illumination(solid lines) with visible light (100 mW cm–2) generated by a 500 W Xe lamp equipped with UV and IR cutoff filters.The CuSCN films were sensitized by readsorbing RB by soaking in a0.5 mM RB aqueous solution for 1 h. The electrolyte was a deaeratedaqueous solution of 0.1 M methylviologen chloride.
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Related In: Results  -  Collection

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Show All Figures
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fig10: I–V curves measured atbulk CuSCN (a) electrodeposited without RB and porous crystallineCuSCN (b) electrodeposited with 1.0 mM RB and RB subsequently removedby DMA treatment, measured in the dark (hashed lines) and under illumination(solid lines) with visible light (100 mW cm–2) generated by a 500 W Xe lamp equipped with UV and IR cutoff filters.The CuSCN films were sensitized by readsorbing RB by soaking in a0.5 mM RB aqueous solution for 1 h. The electrolyte was a deaeratedaqueous solution of 0.1 M methylviologen chloride.
Mentions: We carried out photoelectrochemicalmeasurements on RB-sensitizedporous CuSCN electrodes. The electrodes were the pure CuSCN with arelatively high surface area, that electrodeposited from Cu2+ rich bath without RB, and a highly porous CuSCN made by electrodepositionfrom a SCN– rich bath containing 1.0 mM RB whichthen was removed by the DMA treatment. These electrodes were soakedin an aqueous solution of RB for sensitization. Thus, we prepareda dye-sensitized photocathode with the RB dye shown to undergo photoinducedhole transfer. However, the lack of a suitable redox electrolyte isa significant problem for studying photocathodic sensitization ofCuSCN.5,17 Iodide/triiodide redox electrolyte typicallyused in DSSCs reacts with CuSCN to convert it to CuI that dissolvesrather well in many polar organic solvents. Adsorption of RB moleculesto CuSCN was unfortunately not so stable, as recognized by the factthat the electrolyte solution was clearly colored by desorbed RB bothfor organic and aqueous solutions. For this reason, it was not usefulto use Co complex redox systems, which are kinetically highly reversible,because fast recombination from the uncovered surface of CuSCN orexposed FTO actually killed the voltage under illumination. Stablyadsorbed highly rectifying dyes are needed for effective use of Coredox,6 which are missing at this stage.Thus, we have employed an aqueous solution of methylviologen chlorideas the electron acceptor. The electrode was reasonably stable in thiselectrolyte and exhibited a clear photocathodic action under visiblelight illumination as shown in Figure 10. PureCuSCN film sensitized with RB exhibits about 0.2 V photocurrent onsetvoltage and 22 μA cm–2 photocathodic current;these values increased to ca. 0.3 V and 32 μA cm–2 for the porous CuSCN electrode prepared by hybrid electrodepositionwith RB, extraction of RB, and readsorption of RB. Clearly, enlargedsurface area made the color of the film more intense than that ofthe pure CuSCN, obviously contributing to the increased current. Poorlyrectified dark current for pure CuSCN (Figure 10a) can be associated with the the bare FTO surface being in contactwith the electrolyte, allowing direct charge transfer to methylviologen. Because theporous crystalline CuSCN (Figure 10b) coversthe FTO better than pure CuSCN, the dark current is well-rectifiedand higher voltage is achieved. Despite efforts to find a stable dye–electrolytesolution combination, the RB dye still desorbs from the surface duringmeasurement, likely contributing to the unusually low photocurrent.

Bottom Line: High loading of RB into the film has been achieved to reach a CuSCN:RB volume ratio of approximately 2:1.The crystallographic orientation of the nanostructure with respect to the substrate can be controlled.Photoelectrochemical study on the porous crystalline CuSCN obtained after the DMA treatment and sensitized with RB revealed sensitized photocathodic action under visible light illumination, indicating the potential usefulness of the porous CuSCN electrodes for construction of tandem dye-sensitized solar cells.

View Article: PubMed Central - PubMed

Affiliation: Center of Innovative Photovoltaic Systems (CIPS), Gifu University , Yanagido 1-1, Gifu, Gifu 501-1193, Japan.

ABSTRACT
Nanostructured hybrid thin films of CuSCN and rhodamine B (RB) are electrochemically self-assembled (ESA) by cathodic electrolysis in an ethanol/water mixture containing Cu(2+), SCN(-), and RB. By selecting the solvent, Cu(2+)/SCN(-) ratio, and the concentration of RB, we demonstrate several control parameters in the film formation. High loading of RB into the film has been achieved to reach a CuSCN:RB volume ratio of approximately 2:1. The RB solid could almost completely be extracted from the hybrid film by soaking the film in dimethylacetamide (DMA), leading to a large increase of the surface area. The crystallographic orientation of the nanostructure with respect to the substrate can be controlled. Efficient quenching of fluorescence of RB has been observed for the CuSCN/RB hybrid film, implying hole injection from RB excited state to CuSCN. Photoelectrochemical study on the porous crystalline CuSCN obtained after the DMA treatment and sensitized with RB revealed sensitized photocathodic action under visible light illumination, indicating the potential usefulness of the porous CuSCN electrodes for construction of tandem dye-sensitized solar cells.

No MeSH data available.