Photoelectrochemical activity on Ga-polar and N-polar GaN surfaces for energy conversion

Hsu, Yu‐Kuei; Basilio, Antonio M.; Chen, Yit‐Tsong; Chen, Kuei‐Hsien; Chen, Li‐Chyong

doi:10.1364/oe.22.000a21

Cited by 25 publications

(10 citation statements)

References 20 publications

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“…and surface reactivity are usually considered independent phenomena. [1][2][3] Yet, charge transport within the solid, especially the lateral mobility along the interface, could be influenced significantly by mobile reaction intermediates that accommodate and transport charges along the surface. In a photo-electrochemical cell where the illuminated area is a small part of the total area of the catalytic surface, as is explored with nanoscale geometries, the lateral mobility of charge separated carriers could be especially important for promoting catalysis.…”

mentioning

confidence: 99%

Transient optical diffraction of GaN/aqueous interfaces: Interfacial carrier mobility dependence on surface reactivity

Doan

Pollock

Cuk

2016

Chemical Physics Letters

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While charge transport and surface reactivity have thus far been treated as independent phenomena, the interfacial carrier mobility could be highly dependent on reaction intermediates that carry localized charge and can hop from site to site along the surface. Here, we demonstrate the use of surface sensitive transient optical grating spectroscopy to measure this lateral, interfacial carrier diffusivity at surfaces with different reactivity. We find that for n-GaN, for which substantial charge transfer occurs during equilibration with the water oxidation reaction, the interfacial hole diffusivity increases from air by a factor greater than two under 0.1 M HBr and 0.1 M Na 2 SO 4 aqueous electrolytes.

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confidence: 99%

Transient optical diffraction of GaN/aqueous interfaces: Interfacial carrier mobility dependence on surface reactivity

Doan

Pollock

Cuk

2016

Chemical Physics Letters

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“…However, the photocurrent of PECs II is larger than PECs I when the applied V ext is larger than 0.6 V. The PECs with dodecagon faceted n-GaN electrode have the least and the largest zero bias photocurrent density and voltage at 2 mA/cm 2 , respectively. Lin et al have reported that the polarization direction of GaN would affect the energy band bending of the GaN and electrolytes junction [19]. Ga-polar n-GaN with polarization pointing to GaN would have larger band bending than the N-polar n-GaN with polarization pointing out off the GaN surface.…”

Section: Methodsmentioning

confidence: 99%

“…This trend imparts Ga-polar n-GaN with more effective carrier separation and less carrier recombination than the N-polar n-GaN. Moreover, Jung et al have reported that the surface Fermi level of semipolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) n-GaN/metal contact pinned around 0.82 eV below the conduction band energy [20]. The reduced Schottky barrier height of the semipolar n-GaN/metal contact would suppress the band bending of n-GaN.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, PECs with dodecagon faceted n-GaN electrode have lower zero bias photocurrent density than PECs with smooth surface n-GaN electrode. Fuji revealed the PECs properties on (11-20) nonpolar and (11-22) semipolar n-GaN layer [21], where PECs with (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) nonpolar and (11-22) semipolar n-GaN layer electrodes have lower zero bias photocurrent density than that with (0001) polar n-GaN electrode. However, the photocurrent density (J p )-V ext characteristics of PECs with dodecagon faceted n-GaN electrode could be improved by adding an AlGaN layer.…”

Section: Methodsmentioning

confidence: 99%

“…Surface morphology SEM images of (a) faceted n-GaN, (b) CAC AlGaN/n-GaN, and (c)LGAC AlGaN/GaN electrode (d) The TEM cross-section image cut on the rough surface of the dodecagon faceted n-GaN structure and its corresponding SADP with z = [1-100]. (e) The TEM cross-section image cut on the smooth surface of the dodecagon faceted n-GaN structure and its corresponding SADP with z =[11][12][13][14][15][16][17][18][19][20].…”

mentioning

confidence: 99%

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Photoelectrochemical hydrogen generation with linear gradient Al composition dodecagon faceted AlGaN/n-GaN electrode

Lai¹,

Ma²,

Lin³

et al. 2014

Opt. Express

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We demonstrated photoelectrochemical cells (PECs) with dodecagon faceted AlGaN/n-GaN heterostructure electrode for H(2) generation, where the AlGaN/n-GaN heterostructure has a linear gradient Al composition (LGAC). The separation efficiency of the photo-generated electron-hole pairs in the electrode performs a key function in the H(2) generation efficiency of PEC cells. The linear gradient Al composition, AlGaN, could create more internal field and light absorption because of the linear graded band gap. Therefore, the zero-bias photocurrent density of PEC cells with dodecagon facet LGAC AlGaN/n-GaN heterostructure electrode is around 5.9 times larger than that of dodecagon faceted n-GaN electrode.

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Cobalt‐Phosphate‐Assisted Photoelectrochemical Water Oxidation by Arrays of Molybdenum‐Doped Zinc Oxide Nanorods

et al. 2014

Self Cite

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We report the first demonstration of cobalt phosphate (Co-Pi)-assisted molybdenum-doped zinc oxide nanorods (Zn(1-x)Mo(x)O NRs) as visible-light-sensitive photofunctional electrodes to fundamentally improve the performance of ZnO NRs for photoelectrochemical (PEC) water splitting. A maximum photoconversion efficiency as high as 1.05% was achieved, at a photocurrent density of 1.4 mA cm(-2). More importantly, in addition to achieve the maximum incident photon to current conversion efficiency (IPCE) value of 86%, it could be noted that the IPCE of Zn(1-x)Mo(x)O photoanodes under monochromatic illumination (450 nm) is up to 12%. Our PEC performances are comparable to those of many oxide-based photoanodes in recent reports. The improvement in photoactivity of PEC water splitting may be attributed to the enhanced visible-light absorption, increased charge-carrier densities, and improved interfacial charge-transfer kinetics due to the combined effect of molybdenum incorporation and Co-Pi modification, contributing to photocatalysis. The new design of constructing highly photoactive Co-Pi-assisted Zn(1-x)Mo(x)O photoanodes enriches knowledge on doping and advances the development of high-efficiency photoelectrodes in the solar-hydrogen field.

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Photoelectrochemical activity on Ga-polar and N-polar GaN surfaces for energy conversion

Cited by 25 publications

References 20 publications

Transient optical diffraction of GaN/aqueous interfaces: Interfacial carrier mobility dependence on surface reactivity

Transient optical diffraction of GaN/aqueous interfaces: Interfacial carrier mobility dependence on surface reactivity

Photoelectrochemical hydrogen generation with linear gradient Al composition dodecagon faceted AlGaN/n-GaN electrode

Cobalt‐Phosphate‐Assisted Photoelectrochemical Water Oxidation by Arrays of Molybdenum‐Doped Zinc Oxide Nanorods

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