Extension of Spectral Response of p‐Type Gallium Phosphide Electrodes by Metal Adatoms

Yoneyama, Hiroshi; Mayumi, Shuichi; Tamura, Hideo

doi:10.1149/1.2131398

Cited by 28 publications

(9 citation statements)

References 18 publications

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“…We have Vn~ ~_ --1.0V vs. MSE and the difference ]VH2 --VnFBI ~ 0.8V iS very laPge. A similar phenomenon is observed with many other n-type semiconductors and particularly n-GaP for which a specific interaction with H + ions has been invoked (11). In view of the results Obtained with p-CdTe electrodes, a similar assumption seems possible here.…”

Section: Result~ and Discussionsupporting

confidence: 84%

The Semiconductor‐Electrolyte Interface: Photocurrent and Related Parameters in Cadmium Telluride

Sculfort

Triboulet

Lemasson

1984

J. Electrochem. Soc.

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The normalCdTe‐normalaqueous electrolyte interface is studied both in the dark and under illumination for n‐ and p‐type single crystals. From the anodic and cathodic currents are deduced information about the stability of the semiconductor electrode which agrees fairly well with decomposition potentials calculated from thermodynamic data. For normaln‐normaland p‐normalCdTe , hydrogen evolution prevails to cathodic decomposition. For normaln‐normalCdTe , linear Schottky plots are obtained only after a photoetching in 1MnormalNaOH solution. The flatband potential then measured is consistent with that obtained for normalp‐normalCdTe . Both are pH independent. The minority carrier diffusion length and the Urbach's slope are deduced from photoelectrochemical measurements. They change with the dopant and the free carrier concentration and agree with each other. Information is then obtained about the quality of the samples.

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Section: Result~ and Discussionsupporting

confidence: 84%

The Semiconductor‐Electrolyte Interface: Photocurrent and Related Parameters in Cadmium Telluride

Sculfort

Triboulet

Lemasson

1984

J. Electrochem. Soc.

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“…We assume that the introduction of the Pd layer results in a Schottky barrier electrode structure increasing its current collection efficiency, and that the increase in current collection efficiency due to Pd layer alters the onset potential in spite of the apparently closed flatband potentials. A relatively large extension of spectral range for photoresponse, improved by an outer metal layer, has been reported for p-GaP (19,20) and SrTiO3 (21), Since the spectral photoresponse of the semiconductor itself, such as p-GaP or SrTiO3, is in contrast with this heterojunction electrode, limited to shorter wavelengths, the introduction of surface metal layer is considered to effectively improve spectral photoresponse at longer wavelengths.…”

Section: Resultsmentioning

confidence: 99%

Photoelectrochemical Behavior of Iron Oxide/n‐Si Heterojunction Electrodes with an Outer Pd Layer

Osaka

Ejiri

Hirota

1984

J. Electrochem. Soc.

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Iron oxide/n-Si heterojunction electrodes modified by an outer Pd layer were studied for its utility as an efficient photoanode. The addition of an evaporated Pd layer on the electrode greatly enhanced the photocurrent and shifted the onset potential from 0.5V (Hg-HgO) to the more cathodic side in a 0.2M KOH solution. A 100A Pd layer showed the most cathodic onset potential of -0.36V (Hg-HgO). The unmodified iron oxide/n-Si electrode gave a relatively broad spectral photoresponse with the maximum region lying between 550 and 700 nm. With the addition of the Pd layer the quantum efficiency of spectral photoresponse from 400 to 800 nm became 20% higher. The addition of methanol enhanced the photocurrent up to 1.25 times at 0.6M concentration on the unmodified electrode, whereas on the Pd-modified electrode, the photocurrent decreased slightly by the addition of methanol. These phenomena are discussed in terms of various mechanisms for methanol oxidation.

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“…For experiments where GaP itself was photoexcited, accumulation of electrons at the conduction band edge at the surface apparently reduce surface Ga atoms that could then be reoxidized by sweeping the potential out to sufficiently anodic potentials. Steps 5–7 in Scheme summarize such a process, which is known to occur when there is an absence of efficient acceptors in solution (the native GaP surface is not electrocatalytic for H + reduction at neutral pH). , For charge compensation, this reduction likely drives insertion of H + into the GaP sub-surface. , The net result on the GaP surface is the introduction of new (and likely numerous) chemical defects at the surface.…”

Section: Discussionmentioning

confidence: 99%

“…48,56 For charge compensation, this reduction likely drives insertion of H + into the GaP sub-surface. 55,57 The net result on the GaP surface is the introduction of new (and likely numerous) chemical defects at the surface.…”

Section: ■ Discussionmentioning

confidence: 99%

Sensitization of p-GaP by Physisorbed Triarylmethane Dyes

2018

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p-Type gallium phosphide (GaP) electrodes have been sensitized by triarylmethane dyes physisorbed from aqueous solutions. This work is the first to show light-stimulated hole injection from an adsorbed molecular chromophore on native GaP surfaces. Freshly etched p-GaP(100) and p-GaP(111)A electrodes were loaded with physisorbed dye by brief soaking in solutions of Fast Green. X-ray photoelectron spectroscopy, corroborated by Auger electron spectroscopy, indicated that such treatments yield undetectable surface coverages. However, steady-state photoelectrochemical responses consistently showed that sub-bandgap photoresponses were commensurate with light absorption by the adsorbed dye. The photoresponse characteristics were clearly insensitive to the identity and amount of intended redox mediators dissolved in solution at low light intensities. Instead, the data suggest electrochemically active surface states related to the cathodic degradation of GaP can accept electrons from photoexcited physisorbed dye. Measurements at high illumination intensities showed sensitivity toward redox mediators in solution, indicating that the conventional mode of dye regeneration by redox species in solution is possible with p-GaP. Separate measurements with covalently modified p-GaP(111)A photoelectrodes further suggested that deliberate modification to minimize/eliminate surface states is also possible. Collectively, this work indicates that although some types of dye readily adsorb onto native GaP interfaces, the low dye loadings and the susceptibility of the interface to chemical attack during the sensitization process argue against using bare p-GaP photocathodes with physisorbed triarylmethane dyes. Instead, these studies suggest that dye-sensitized photocathodes based on p-GaP require deliberate surface chemical modification methods to overcome the low loading and inhibit unwanted charge transfer between the surface and the photoexcited dye.

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Extension of Spectral Response of p‐Type Gallium Phosphide Electrodes by Metal Adatoms

Cited by 28 publications

References 18 publications

The Semiconductor‐Electrolyte Interface: Photocurrent and Related Parameters in Cadmium Telluride

The Semiconductor‐Electrolyte Interface: Photocurrent and Related Parameters in Cadmium Telluride

Photoelectrochemical Behavior of Iron Oxide/n‐Si Heterojunction Electrodes with an Outer Pd Layer

Sensitization of p-GaP by Physisorbed Triarylmethane Dyes

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