High Density n-Si/n-TiO<sub>2</sub>Core/Shell Nanowire Arrays with Enhanced Photoactivity

Hwang, Yun Jeong; Boukai, Akram; Yang, Peidong

doi:10.1021/nl8032763

Cited by 550 publications

(520 citation statements)

References 33 publications

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“…These features demonstrate great potential for photoelectrochemical purposes. In agreement with the literature [25] for a n-Si/n-TiO 2 heterojunction, the photogenerated holes under positive bias potential move toward the n-TiO2/electrolyte interface where oxidation reaction takes place. Therefore, the photogenerated electrons in the n-Si move to the counter electrode, where the reduction reaction takes place.…”

Section: Introductionsupporting

confidence: 90%

“…However, this material has poor chemical stability and can be easily oxidized in aqueous solution under applied potential [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

“…The metal grid combination with a bias potential facilitated the transport of holes from the Si to the TiO 2 surface, and the spill over from the TiO 2 to the metal grid, culminating in the generation of active chemical species at the semiconductor surface [27]. The semiconductor heterojunction of p-Si/TiO 2 has different band bending properties near the junction [25], which enhances the charge separation and minimize recombination within the material. This behavior enhances the possibility of increasing electrons flow at the material semiconductor surface.…”

Section: Introductionmentioning

confidence: 99%

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A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

Guaraldo

Brito

Wood

et al. 2015

Electrochimica Acta

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Section: Introductionsupporting

confidence: 90%

“…However, this material has poor chemical stability and can be easily oxidized in aqueous solution under applied potential [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

Guaraldo

Brito

Wood

et al. 2015

Electrochimica Acta

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“…28 Therefore, we chose to n-type dope the Si wire arrays with phosphorus since the as-grown InGaN nanowires are n-type. Post-growth doping of the Si wires could also create a better electron conducting pathway for charge collection.…”

Section: Introductionmentioning

confidence: 99%

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

et al. 2012

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Three dimensional hierarchical nanostructures were synthesized by the halide chemical vapor deposition (HCVD) of InGaN nanowires on Si wire arrays. Single phase InGaN nanowires grew vertically on the sidewalls of Si wires and acted as a high surface area photoanode for solar water splitting. Electrochemical measurements showed that the photocurrent density with hierarchical Si/InGaN nanowire arrays increased by 5 times compared to the photocurrent density with InGaN nanowire arrays grown on planar Si (1.23 V vs RHE). High resolution transmission electron microscopy showed that InGaN nanowires are stable after 15 hours of illumination. These measurements show that Si/InGaN hierarchical nanostructures are a viable high surface area geometry for stable solar water splitting. KEYWORDS:Hierarchical nanostructure, InGaN nanowire, Si wire, photoanode, solar water splitting IntroductionPhotolysis of water with semiconductor materials has been investigated as a clean and renewable energy conversion process by storing solar energy in chemical bonds such as hydrogen. [1][2][3] Since Fujishima and Honda 4 reported the capability of water splitting with TiO 2 , metal oxide semiconductors have been studied extensively due to their stability under photo-anodic conditions. [5][6] However, the valence band of metal oxide semiconductors consists mainly of O 2p orbitals resulting in a low energy maximum (around +3 V vs NHE compared to +1.23 V vs NHE for the water oxidation reaction). This leads to a significant loss in energy from the large difference in potential between the valence band and water oxidation reaction. In addition, lowering the metal oxide bandgap energy for visible light absorption generally comes at the cost of moving the conduction band minimum (CBM) towards lower potentials than the hydrogen reduction potential which cannot perform spontaneous solar water splitting.On the other hand, metal nitrides have less positive valence band maximum (VBM) potentials than metal oxides because N 2p orbitals have smaller ionization energies than O 2p orbitals. [6][7] For example, GaN is one of the nitride semiconductors that have been studied for photocatalytic applications [8][9][10][11] because its CBM and VBM straddle the hydrogen reduction (H + /H 2 ) and water oxidation (H 2 O/O 2 ) potentials. Although GaN has a large bandgap (3.4 eV), indium alloying to form InGaN can tune the bandgap from the ultraviolet to the near infrared region 12 encompassing the entire solar spectrum. The In 0.5 Ga 0.5 N alloy has a bandgap of around 2.0 eV which is desirable for overall water splitting considering the overpotential for the water oxidation reaction. [13][14] Moses et al. 15 calculated that the VBM of InGaN alloy increases in energy almost linearly with indium composition. Therefore, the InGaN alloy was suggested to accomplish spontaneous overall water splitting with up to 50% indium incorporation since both the CBM and VBM can satisfy the energetic requirements. Experimentally, single crystalline In x Ga 1-x N nanowire...

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“…Especially, the metal oxide film like titanium dioxide (TiO 2 ) has been studied widely as a photovoltaic material. The heterojunction solar cells consisting of n-type TiO 2 and various semiconducting materials have been reported [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Much attention is focused on the research to develop flexible solar cells, where a plastic substrate and a transparent conducting film such as an indium-tin-oxide (ITO)-coating film are mostly used.…”

Section: Introductionmentioning

confidence: 99%

Heterojunctions of TiO2 nanoparticle film and c-Si with different Fermi level positions

Watanabe

Qin

2014

Appl. Phys. A

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The photovoltaic properties of heterojunctions of titanium dioxide (TiO 2 ) nanoparticle films with single crystal silicon (c-Si) substrates with different Fermi level (E f ) positions were studied. The TiO 2 nanoparticles of rutile and anatase structures were studied without any sintering process. To clarify the photovoltaic properties, the characteristics of the heterojunction solar cells of TiO 2 nanoparticle films with p-Si and n-Si substrates were investigated, where several Si substrates with different resistivities were used. The I-V characteristics of p-Si/TiO 2 heterojunction showed the rectifying behavior and photovoltaic effect. The n-Si/TiO 2 heterojunction also showed good rectifying characteristics; however, the conversion efficiency was extremely lower than that of p-Si/TiO 2 heterojunction. The conversion efficiencies of various Si/TiO 2 (rutile) heterojunction solar cells against the Fermi level E f of c-Si showed the maximum in the p-doped region. The photovoltaic properties of the Si/TiO 2 heterojunction also depended on the crystal structure of TiO 2 , and the conversion efficiency of anatase is higher than that of rutile, which was attributed to the higher carrier mobility of anatase.

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High Density n-Si/n-TiO₂Core/Shell Nanowire Arrays with Enhanced Photoactivity

Cited by 550 publications

References 33 publications

A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

Heterojunctions of TiO2 nanoparticle film and c-Si with different Fermi level positions

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High Density n-Si/n-TiO2Core/Shell Nanowire Arrays with Enhanced Photoactivity

Cited by 550 publications

References 33 publications

A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

Heterojunctions of TiO2 nanoparticle film and c-Si with different Fermi level positions

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High Density n-Si/n-TiO₂Core/Shell Nanowire Arrays with Enhanced Photoactivity