Hyun Soo (Eric) Han
Senior Physical Science Research Scientist
Mechanical Engineering
Academic Appointments
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Sr Res Scientist-Physical, Mechanical Engineering
All Publications
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Dual textured BiVO4/Sb:SnO2 heterostructure for enhanced photoelectrochemical Water-splitting
CHEMICAL ENGINEERING JOURNAL
2022; 435
View details for DOI 10.1016/j.cej.2022.135183
View details for Web of Science ID 000773622300005
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Improving intrinsic oxygen reduction activity and stability: Atomic layer deposition preparation of platinum-titanium alloy catalysts
APPLIED CATALYSIS B-ENVIRONMENTAL
2022; 300
View details for DOI 10.1016/j.apcatb.2021.120741
View details for Web of Science ID 000707873700001
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Enhancing Solar Water Splitting of Textured BiVO4 by Dual Effect of a Plasmonic Silver Nanoshell: Plasmon-Induced Light Absorption and Enhanced Hole Transport
ACS APPLIED ENERGY MATERIALS
2020; 3 (12): 11886–92
View details for DOI 10.1021/acsaem.0c02001
View details for Web of Science ID 000618839200042
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Condensing water vapor to droplets generates hydrogen peroxide.
Proceedings of the National Academy of Sciences of the United States of America
2020
Abstract
It was previously shown [J. K. Lee et al., Proc. Natl. Acad. Sci. U.S.A, 116, 19294-19298 (2019)] that hydrogen peroxide (H2O2) is spontaneously produced in micrometer-sized water droplets (microdroplets), which are generated by atomizing bulk water using nebulization without the application of an external electric field. Here we report that H2O2 is spontaneously produced in water microdroplets formed by dropwise condensation of water vapor on low-temperature substrates. Because peroxide formation is induced by a strong electric field formed at the water-air interface of microdroplets, no catalysts or external electrical bias, as well as precursor chemicals, are necessary. Time-course observations of the H2O2 production in condensate microdroplets showed that H2O2 was generated from microdroplets with sizes typically less than 10 m. The spontaneous production of H2O2 was commonly observed on various different substrates, including silicon, plastic, glass, and metal. Studies with substrates with different surface conditions showed that the nucleation and the growth processes of condensate water microdroplets govern H2O2 generation. We also found that the H2O2 production yield strongly depends on environmental conditions, including relative humidity and substrate temperature. These results show that the production of H2O2 occurs in water microdroplets formed by not only atomizing bulk water but also condensing water vapor, suggesting that spontaneous water oxidation to form H2O2 from water microdroplets is a general phenomenon. These findings provide innovative opportunities for green chemistry at heterogeneous interfaces, self-cleaning of surfaces, and safe and effective disinfection. They also may have important implications for prebiotic chemistry.
View details for DOI 10.1073/pnas.2020158117
View details for PubMedID 33229543
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Boosting the solar water oxidation performance of a BiVO4 photoanode by crystallographic orientation control
ENERGY & ENVIRONMENTAL SCIENCE
2018; 11 (5): 1299–1306
View details for DOI 10.1039/c8ee00125a
View details for Web of Science ID 000432599100017
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Activating and optimizing MoS2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies (vol 15, pg 48, 2016)
NATURE MATERIALS
2016; 15 (3)
View details for DOI 10.1038/NMAT4564
View details for Web of Science ID 000370967400024
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Unique photothermal material: Copper phosphate (Cu<sub>3</sub>P<sub>2</sub>O<sub>8</sub>) with broadband visible-to-near-infrared absorption properties for efficient solar steam generation
DESALINATION
2024; 579
View details for DOI 10.1016/j.desal.2024.117464
View details for Web of Science ID 001206274400001
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Bimetallic NiO/NiFe2O4 heterostructures with interfacial effects for boosting electrochemical water splitting applications
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
2024; 952
View details for DOI 10.1016/j.jelechem.2023.117947
View details for Web of Science ID 001132367100001
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Ultralow-Overpotential Acidic Oxygen Evolution Reaction Over Bismuth Telluride-Carbon Nanotube Heterostructure with Organic Framework.
Small (Weinheim an der Bergstrasse, Germany)
2023: e2307059
Abstract
The state-of-the-art iridium and ruthenium oxides-based materials are best known for high efficiency and stability in acidic oxygen evolution reaction (OER). However, the development of economically feasible catalysts for water-splitting technologies is challenging by the requirements of low overpotential, high stability, and resistance of catalysts to dissolution during the acidic oxygen evolution reaction . Herein, an organometallic core-shell heterostructure composed of a carbon nanotube core (CNT) and bismuth telluride (Bi2 Te3 ) shell (denoted as nC-Bi2 Te3 ) is designed and use it as a catalyst for the acidic OER. The proposed catalyst achieves an ultralow overpotential of 160 mV at 10 mA cm-2 (geometrical), thereby outperforming most of the state-of-the-art precious-metal-based catalysts. The low Tafel slope of 30 mV dec-1 and charge transfer resistance (RCT ) of 1.5 Ω demonstrate its excellent electrocatalytic activity. The morphological and chemical compositions of nC-Bi2 Te3 enable the generation of ─OH functional group in the Bi─Te sections formed via a ligand support, which enhances the absorption capacity of H+ ions and increases the intrinsic catalytic activity. The presented insights regarding the material composition-structure relationship can help expand the application scope of high-performance catalysts.
View details for DOI 10.1002/smll.202307059
View details for PubMedID 37946687
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<span contenteditable="false" data-cke-magic-line="1" style="width: 636px; height: 0px; padding: 0px; margin: 0px; display: block; z-index: 9999; color: rgb(255,255,255); font-size: 0px; line-height: 0px; position: absolute; border-top: 1px dashed rgb(255,0,0); user-select: none; left:-1.48148px; top: 65.213px;"><span style="color:#ffffff">& nbsp;</span><span style="color:#ffffff">& nbsp;</span><span style="color:#ffffff">?</span></span>In situ decorated Cu2FeSnS4 nanosheet arrays for low voltage hydrogen production through the ammonia oxidation reaction
MATERIALS CHEMISTRY FRONTIERS
2023
View details for DOI 10.1039/d3qm00291h
View details for Web of Science ID 001069637400001
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Expanded solar absorption spectrum to improve photoelectrochemical oxygen evolution reaction: Synergistic effect of upconversion nanoparticles and ZnFe2O4/TiO2
CHEMICAL ENGINEERING JOURNAL
2022; 438
View details for DOI 10.1016/j.cej.2022.135503
View details for Web of Science ID 000779681800002
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Sharp-edged nanoflakes array of CuO with enhanced optical and charge transport properties for Bias-Free tandem solar Water-splitting
APPLIED SURFACE SCIENCE
2022; 585
View details for DOI 10.1016/j.apsusc.2022.152632
View details for Web of Science ID 000776697400002
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Facile fabrication of nanotubular heterostructure for enhanced photoelectrochemical performance
CERAMICS INTERNATIONAL
2021; 47 (3): 3972–77
View details for DOI 10.1016/j.ceramint.2020.09.261
View details for Web of Science ID 000603042400002
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(020)-Textured tungsten trioxide nanostructure with enhanced photoelectrochemical activity
JOURNAL OF CATALYSIS
2020; 389: 328–36
View details for DOI 10.1016/j.jcat.2020.06.012
View details for Web of Science ID 000566793000003
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Fabrication of an ingenious metallic asymmetric supercapacitor by the integration of anodic iron oxide and cathodic nickel phosphide
APPLIED SURFACE SCIENCE
2020; 511
View details for DOI 10.1016/j.apsusc.2020.145424
View details for Web of Science ID 000517883800031
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Retarded Charge-Carrier Recombination in Photoelectrochemical Cells from Plasmon-Induced Resonance Energy Transfer
ADVANCED ENERGY MATERIALS
2020
View details for DOI 10.1002/aenm.202000570
View details for Web of Science ID 000527995600001
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Tunable Dielectric and Thermal Properties of Oxide Dielectrics via Substrate Biasing in Plasma-Enhanced Atomic Layer Deposition.
ACS applied materials & interfaces
2020
Abstract
The ability to control the properties of dielectric thin films on demand is of fundamental interest in nanoscale devices. Here, we modulate plasma characteristics at the surface of a substrate to tune both dielectric constant and thermal conductivity of amorphous thin films grown using plasma-enhanced atomic layer deposition. Specifically, we apply a substrate bias ranging from 0 to ∼117 V and demonstrate the systematic tunability of various material parameters of Al2O3. As a function of the substrate bias, we find a nonmonotonical evolution of intrinsic properties, including density, dielectric constant, and thermal conductivity. A key observation is that the maximum values in dielectric constant and effective thermal conductivity emerge at different substrate biases. The impact of density on both thermal conductivity and dielectric constant is further examined using a differential effective medium theory and the Clausius-Mossotti model, respectively. We find that the peak value in the dielectric constant deviates from the Clausius-Mossotti model, indicating the change of oxygen fraction in our thin films as a function of substrate bias. This finding suggests that the increased local strength of plasma sheath not only enhances material density but also controls the dynamics of microstructural defect formation beyond what is possible with conventional approaches. Based on our experimental observations and modeling, we further build a phenomenological relation between dielectric constant and thermal conductivity. Our results pave invaluable avenues for optimizing dielectric thin films at the atomic scale for a wide range of applications in nanoelectronics and energy devices.
View details for DOI 10.1021/acsami.0c11086
View details for PubMedID 32915545
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Photo-annealed amorphous titanium oxide for perovskite solar cells.
Nanoscale
2019
Abstract
Electron selective layers are important to the efficiency, stability and hysteresis of perovskite solar cells. Photo-annealing is a low-cost, roll-to-roll-compatible process that can be applied to the post-treatment fabrication of sol-gel based metal oxide layers. Here, we fabricate an amorphous titanium oxide electron selective layer at a low temperature in a dry atmosphere using a UV light annealing system and compare it with a thermal annealing process. Active oxygen species are created by using UV light to promote hydrolysis and condense the TiO2 precursor, which removes organic ligands effectively. The photo-annealed TiO2-based perovskite solar cell has a power conversion efficiency of 19.37% without hysteresis.
View details for DOI 10.1039/c9nr05776e
View details for PubMedID 31552996
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Spontaneous generation of hydrogen peroxide from aqueous microdroplets.
Proceedings of the National Academy of Sciences of the United States of America
2019
Abstract
We show H2O2 is spontaneously produced from pure water by atomizing bulk water into microdroplets (1 mum to 20 m in diameter). Production of H2O2, as assayed by H2O2-sensitve fluorescence dye peroxyfluor-1, increased with decreasing microdroplet size. Cleavage of 4-carboxyphenylboronic acid and conversion of phenylboronic acid to phenols in microdroplets further confirmed the generation of H2O2 The generated H2O2 concentration was 30 M (1 part per million) as determined by titration with potassium titanium oxalate. Changing the spray gas to O2 or bubbling O2 decreased the yield of H2O2 in microdroplets, indicating that pure water microdroplets directly generate H2O2 without help from O2 either in air surrounding the droplet or dissolved in water. We consider various possible mechanisms for H2O2 formation and report a number of different experiments exploring this issue. We suggest that hydroxyl radical (OH) recombination is the most likely source, in which OH is generated by loss of an electron from OH- at or near the surface of the water microdroplet. This catalyst-free and voltage-free H2O2 production method provides innovative opportunities for green production of hydrogen peroxide.
View details for DOI 10.1073/pnas.1911883116
View details for PubMedID 31451646
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Boosting the solar water oxidation performance of a BiVO4 photoanode by crystallographic orientation control (vol 11, pg 1299, 2018)
ENERGY & ENVIRONMENTAL SCIENCE
2019; 12 (4): 1427
View details for DOI 10.1039/c9ee90017a
View details for Web of Science ID 000465275800023
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Point defect-reduced colloidal SnO2 electron transport layers for stable and almost hysteresis-free perovskite solar cells.
RSC advances
2019; 9 (13): 7334-7337
Abstract
The commercialization of perovskite solar cells has been investigated, but the instability of their light-absorbing layers remains a problem. We demonstrate that the use of colloidal SnO2 nanoparticles prevents perovskite light absorber decomposition, reduces the hysteresis index to 0.1%, and increases the power conversion efficiency to 19.12%.
View details for DOI 10.1039/c9ra00366e
View details for PubMedID 35519987
View details for PubMedCentralID PMC9061193
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Point defect-reduced colloidal SnO2 electron transport layers for stable and almost hysteresis-free perovskite solar cells
RSC ADVANCES
2019; 9 (13): 7334–37
View details for DOI 10.1039/c9ra00366e
View details for Web of Science ID 000462644300038
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Facile and controllable surface-functionalization of TiO2 nanotubes array for highly-efficient photoelectrochemical water-oxidation
JOURNAL OF CATALYSIS
2018; 365: 138–44
View details for DOI 10.1016/j.jcat.2018.06.022
View details for Web of Science ID 000442976400016
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Enhancing Mo:BiVO4 Solar Water Splitting with Patterned Au Nanospheres by Plasmon-Induced Energy Transfer
ADVANCED ENERGY MATERIALS
2018; 8 (5)
View details for DOI 10.1002/aenm.201701765
View details for Web of Science ID 000425113600016
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Electrochemical generation of sulfur vacancies in the basal plane of MoS2 for hydrogen evolution
NATURE COMMUNICATIONS
2017; 8
Abstract
Recently, sulfur (S)-vacancies created on the basal plane of 2H-molybdenum disulfide (MoS2) using argon plasma exposure exhibited higher intrinsic activity for the electrochemical hydrogen evolution reaction than the edge sites and metallic 1T-phase of MoS2 catalysts. However, a more industrially viable alternative to the argon plasma desulfurization process is needed. In this work, we introduce a scalable route towards generating S-vacancies on the MoS2 basal plane using electrochemical desulfurization. Even though sulfur atoms on the basal plane are known to be stable and inert, we find that they can be electrochemically reduced under accessible applied potentials. This can be done on various 2H-MoS2 nanostructures. By changing the applied desulfurization potential, the extent of desulfurization and the resulting activity can be varied. The resulting active sites are stable under extended desulfurization durations and show consistent HER activity.
View details for DOI 10.1038/ncomms15113
View details for Web of Science ID 000399985300001
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One-Step Hydrothermal Deposition of Ni:FeOOH onto Photoanodes for Enhanced Water Oxidation
ACS ENERGY LETTERS
2016; 1 (3): 624-632
View details for DOI 10.1021/acsenergylett.6b00303
View details for Web of Science ID 000389617900023
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Indium-Tin-Oxide Nanowire Array Based CdSe/CdS/TiO2 One-Dimensional Heterojunction Photoelectrode for Enhanced Solar Hydrogen Production
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
2016; 4 (3): 1161-1168
View details for DOI 10.1021/acssuschemeng.5b01229
View details for Web of Science ID 000371755400065
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Enhancing Low-Bias Performance of Hematite Photoanodes for Solar Water Splitting by Simultaneous Reduction of Bulk, Interface, and Surface Recombination Pathways
ADVANCED ENERGY MATERIALS
2016; 6 (4)
View details for DOI 10.1002/aenm.201501840
View details for Web of Science ID 000371147000011
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CdS-sensitized 1-D single-crystalline anatase TiO2 nanowire arrays for photoelectrochemical hydrogen production
1st International Conference on Nanotechnology, Nanomaterials and Thin Films for Energy Applications (Nano Energy)
PERGAMON-ELSEVIER SCIENCE LTD. 2015: 863–69
View details for DOI 10.1016/j.ijhydene.2014.09.174
View details for Web of Science ID 000348687300089
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Facile Preparation of TiO2 Nanobranch/Nanoparticle Hybrid Architecture with Enhanced Light Harvesting Properties for Dye-Sensitized Solar Cells
JOURNAL OF NANOMATERIALS
2015
View details for DOI 10.1155/2015/139715
View details for Web of Science ID 000364687400001
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Ta-substituted SnNb2-xTaxO6 photocatalysts for hydrogen evolution under visible light irradiation
JOURNAL OF MATERIALS CHEMISTRY A
2015; 3 (2): 825-831
View details for DOI 10.1039/c4ta05885b
View details for Web of Science ID 000346082100046
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A tree-like nanoporous WO3 photoanode with enhanced charge transport efficiency for photoelectrochemical water oxidation
JOURNAL OF MATERIALS CHEMISTRY A
2015; 3 (24): 12920-12926
View details for DOI 10.1039/c5ta00823a
View details for Web of Science ID 000356022800043
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Nanostructured Ti-doped hematite (alpha-Fe2O3) photoanodes for efficient photoelectrochemical water oxidation
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
2014; 39 (30): 17501-17507
View details for DOI 10.1016/j.ijhydene.2013.10.031
View details for Web of Science ID 000343839000079
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In2O3:Sn/TiO2/CdS heterojunction nanowire array photoanode in photoelectrochemical cells
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
2014; 39 (30): 17473-17480
View details for DOI 10.1016/j.ijhydene.2013.12.087
View details for Web of Science ID 000343839000075
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Heterojunction Fe2O3-SnO2 Nanostructured Photoanode for Efficient Photoelectrochemical Water Splitting
JOM
2014; 66 (4): 664-669
View details for DOI 10.1007/s11837-014-0915-1
View details for Web of Science ID 000335503400018
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A Hierarchically Organized Photoelectrode Architecture for Highly Efficient CdS/CdSe-Sensitized Solar Cells
ADVANCED ENERGY MATERIALS
2014; 4 (3)
View details for DOI 10.1002/aenm.201300395
View details for Web of Science ID 000331709900012
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Direct Printing Synthesis of Self-Organized Copper Oxide Hollow Spheres on a Substrate Using Copper(II) Complex Ink: Gas Sensing and Photoelectrochemical Properties
LANGMUIR
2014; 30 (3): 700-709
Abstract
The direct printing synthesis of metal oxide hollow spheres in the form of film on a substrate is reported for the first time. This method offers facile, scalable, high-throughput production and device fabrication processes. The printing was carried out via a doctor-blade method using Cu(II) complex ink with controllable high viscosity based on formate-amine coupling. Following only thermal heating in air, well-defined polycrystalline copper oxide hollow spheres with a submicrometer diameter (≤1 μm) were formed spontaneously while being assembled in the form of a film with good adhesion on the substrate. This spontaneous hollowing mechanism was found to result from the Kirkendall effect during oxidation at elevated temperature. The CuO films with hollow spheres, prepared via direct printing synthesis at 500 °C, led to the creation of a superior p-type gas sensor and photocathode for photoelectrochemical water splitting with completely hollow cores, a rough/porous shell structure, a single phase, high crystallinity, and no organic/polymer residue. As a result, the CuO hollow-sphere films showed high gas responses and permissible response speeds to reducing gases and high photocurrent density compared to conventional CuO powder films and the values previously reported. These results exemplify the successful realization of a high-throughput printing fabrication method for the creation of superior nanostructured devices.
View details for DOI 10.1021/la404098s
View details for Web of Science ID 000330543700004
View details for PubMedID 24422661
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1-D Structured Flexible Supercapacitor Electrodes with Prominent Electronic/Ionic Transport Capabilities
ACS APPLIED MATERIALS & INTERFACES
2014; 6 (1): 268-274
Abstract
A highly efficient 1-D flexible supercapacitor with a stainless steel mesh (SSM) substrate is demonstrated. Indium tin oxide (ITO) nanowires are prepared on the surface of the stainless steel fiber (SSF), and MnO2 shell layers are coated onto the ITO/SSM electrode by means of electrodeposition. The ITO NWs, which grow radially on the SSF, are single-crystalline and conductive enough for use as a current collector for MnO2-based supercapacitors. A flake-shaped, nanoporous, and uniform MnO2 shell layer with a thickness of ~130 nm and an average crystallite size of ~2 nm is obtained by electrodeposition at a constant voltage. The effect of the electrode geometry on the supercapacitor properties was investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and a galvanostatic charge/discharge study. The electrodes with ITO NWs exhibit higher specific capacitance levels and good rate capability owing to the superior electronic/ionic transport capabilities resulting from the open pore structure. Moreover, the use of a porous mesh substrate (SSM) increases the specific capacitance to 667 F g(-1) at 5 mV s(-1). In addition, the electrode with ITO NWs and the SSM shows very stable cycle performance (no decrease in the specific capacitance after 5000 cycles).
View details for DOI 10.1021/am404132j
View details for Web of Science ID 000329586300037
View details for PubMedID 24397749
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Surface-area-tuned, quantum-dot-sensitized heterostructured nanoarchitectures for highly efficient photoelectrodes
NANO RESEARCH
2014; 7 (1): 144-153
View details for DOI 10.1007/s12274-013-0381-z
View details for Web of Science ID 000329793800011
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TiO2 nanocrystals shell layer on highly conducting indium tin oxide nanowire for photovoltaic devices (vol 5, pg 3520, 2013)
NANOSCALE
2013; 5 (24): 12674-12674
View details for Web of Science ID 000327507900091
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Aligned Photoelectrodes with Large Surface Area Prepared by Pulsed Laser Deposition
JOURNAL OF PHYSICAL CHEMISTRY C
2012; 116 (14): 8102-8110
View details for DOI 10.1021/jp211233s
View details for Web of Science ID 000302591300063
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Facile hydrothermal synthesis of InVO4 microspheres and their visible-light photocatalytic activities
MATERIALS LETTERS
2012; 72: 98-100
View details for DOI 10.1016/j.matlet.2011.12.013
View details for Web of Science ID 000301213000028
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Tin doped indium oxide core-TiO2 shell nanowires on stainless steel mesh for flexible photoelectrochemical cells
APPLIED PHYSICS LETTERS
2012; 100 (8)
View details for DOI 10.1063/1.3684805
View details for Web of Science ID 000300711200074
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Nanowire-Based Three-Dimensional Transparent Conducting Oxide Electrodes for Extremely Fast Charge Collection
ADVANCED ENERGY MATERIALS
2011; 1 (5): 829-835
View details for DOI 10.1002/aenm.201100241
View details for Web of Science ID 000295140100018
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A Newly Designed Nb-Doped TiO2/Al-Doped ZnO Transparent Conducting Oxide Multi layer for Electrochemical Photoenergy Conversion Devices
JOURNAL OF PHYSICAL CHEMISTRY C
2010; 114 (32): 13867-13871
View details for DOI 10.1021/jp104247t
View details for Web of Science ID 000280727500064
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Tailoring the Morphology and Structure of Nanosized Zn2SiO4: Mn2+ Phosphors Using the Hydrothermal Method and Their Luminescence Properties
JOURNAL OF PHYSICAL CHEMISTRY C
2010; 114 (23): 10330-10335
View details for DOI 10.1021/jp911731s
View details for Web of Science ID 000278479700002
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Enhancing the Densification of Nanocrystalline TiO2 by Reduction in Spark Plasma Sintering
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
2010; 93 (4): 993-997
View details for DOI 10.1111/j.1551-2916.2009.03529.x
View details for Web of Science ID 000276246700020
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Photoluminescence and electrical properties of epitaxial Al-doped ZnO transparent conducting thin films
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
2009; 206 (9): 2133-2138
View details for DOI 10.1002/pssa.200881790
View details for Web of Science ID 000270440100037
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Nb-Doped TiO2: A New Compact Layer Material for TiO2 Dye-Sensitized Solar Cells
JOURNAL OF PHYSICAL CHEMISTRY C
2009; 113 (16): 6878-6882
View details for DOI 10.1021/jp9002017
View details for Web of Science ID 000265383300074
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Functional Multilayered Transparent Conducting Oxide Thin Films for Photovoltaic Devices
JOURNAL OF PHYSICAL CHEMISTRY C
2009; 113 (3): 1083-1087
View details for DOI 10.1021/jp808279j
View details for Web of Science ID 000262522000040