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Xudong Wang - One of the best experts on this subject based on the ideXlab platform.
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simultaneous enhancement of Charge Separation and hole transportation in a tio2 srtio3 core shell nanowire photoelectrochemical system
Advanced Materials, 2017Co-Authors: Fei Wu, Yanhao Yu, Huang Yang, Lazarus N German, Zhenquan Li, Jianguo Chen, Weiguang Yang, Lu Huang, Linjun Wang, Xudong WangAbstract:Efficient Charge Separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of Charge Separation and hole transportation on the basis of ferroelectric polarization in TiO2–SrTiO3 core–shell nanowires (NWs) is reported. The SrTiO3 shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO2. Combined with its intrinsically high Charge mobility, the ferroelectric SrTiO3 thin shell significantly improves the Charge-Separation efficiency (ηSeparation) with minimized influence on the hole-migration property of TiO2 photoelectrodes, leading to a drastically increased photocurrent density ( Jph). Specifically, the 10 nm-thick SrTiO3 shell yields the highest Jph and ηSeparation of 1.43 mA cm−2 and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO2 NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO3 film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the Charge-Separation and hole-transportation properties.
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simultaneous enhancement of Charge Separation and hole transportation in a tio2 srtio3 core shell nanowire photoelectrochemical system
Advanced Materials, 2017Co-Authors: Huang Yang, Lazarus N German, Jianguo Chen, Weiguang Yang, Lu Huang, Linjun Wang, Weimin Shi, Xudong WangAbstract:Efficient Charge Separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of Charge Separation and hole transportation on the basis of ferroelectric polarization in TiO2–SrTiO3 core–shell nanowires (NWs) is reported. The SrTiO3 shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO2. Combined with its intrinsically high Charge mobility, the ferroelectric SrTiO3 thin shell significantly improves the Charge-Separation efficiency (ηSeparation) with minimized influence on the hole-migration property of TiO2 photoelectrodes, leading to a drastically increased photocurrent density ( Jph). Specifically, the 10 nm-thick SrTiO3 shell yields the highest Jph and ηSeparation of 1.43 mA cm−2 and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO2 NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO3 film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the Charge-Separation and hole-transportation properties.
Huang Yang - One of the best experts on this subject based on the ideXlab platform.
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simultaneous enhancement of Charge Separation and hole transportation in a tio2 srtio3 core shell nanowire photoelectrochemical system
Advanced Materials, 2017Co-Authors: Fei Wu, Yanhao Yu, Huang Yang, Lazarus N German, Zhenquan Li, Jianguo Chen, Weiguang Yang, Lu Huang, Linjun Wang, Xudong WangAbstract:Efficient Charge Separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of Charge Separation and hole transportation on the basis of ferroelectric polarization in TiO2–SrTiO3 core–shell nanowires (NWs) is reported. The SrTiO3 shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO2. Combined with its intrinsically high Charge mobility, the ferroelectric SrTiO3 thin shell significantly improves the Charge-Separation efficiency (ηSeparation) with minimized influence on the hole-migration property of TiO2 photoelectrodes, leading to a drastically increased photocurrent density ( Jph). Specifically, the 10 nm-thick SrTiO3 shell yields the highest Jph and ηSeparation of 1.43 mA cm−2 and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO2 NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO3 film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the Charge-Separation and hole-transportation properties.
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simultaneous enhancement of Charge Separation and hole transportation in a tio2 srtio3 core shell nanowire photoelectrochemical system
Advanced Materials, 2017Co-Authors: Huang Yang, Lazarus N German, Jianguo Chen, Weiguang Yang, Lu Huang, Linjun Wang, Weimin Shi, Xudong WangAbstract:Efficient Charge Separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of Charge Separation and hole transportation on the basis of ferroelectric polarization in TiO2–SrTiO3 core–shell nanowires (NWs) is reported. The SrTiO3 shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO2. Combined with its intrinsically high Charge mobility, the ferroelectric SrTiO3 thin shell significantly improves the Charge-Separation efficiency (ηSeparation) with minimized influence on the hole-migration property of TiO2 photoelectrodes, leading to a drastically increased photocurrent density ( Jph). Specifically, the 10 nm-thick SrTiO3 shell yields the highest Jph and ηSeparation of 1.43 mA cm−2 and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO2 NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO3 film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the Charge-Separation and hole-transportation properties.
Tianquan Lian - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast Charge Separation in Two-Dimensional CsPbBr3 Perovskite Nanoplatelets
2019Co-Authors: Tianquan LianAbstract:Two-dimensional (2D) cesium lead halide perovskite colloidal nanoplatelets show sharper excitonic absorption/emission peaks and larger absorption cross section in comparison to bulk materials and quantum dots. It remains unclear how 2D exciton and Charge Separation properties can be utilized to further enhance the performance of perovskite materials for optoelectrical applications. Herein, we report a study of exciton and interfacial Charge-transfer dynamics of CsPbBr3 nanoplatelets via transient absorption spectroscopy. The exciton binding energy (∼260 meV) is determined via detailed spectral analysis. The exciton bleach is caused by band-edge exciton state-filling with negligible single carrier (electron or hole) contributions. Efficient Charge Separation can be achieved by selective electron and hole transfers to adsorbed molecular acceptors (benzoquinone and phenothiazine, respectively), and the half-life of the Charge-separated state (≫100 ns) in nanoplatelet-phenothiazine complexes is >100 fold longer than that in quantum dot-phenothiazine complexes. Our results suggest that CsPbBr3 nanoplatelets are promising materials for photocatalysis and photovoltaic applications
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wavefunction engineering in quantum confined semiconductor nanoheterostructures for efficient Charge Separation and solar energy conversion
Energy and Environmental Science, 2012Co-Authors: Haiming Zhu, Tianquan LianAbstract:Colloidal quantum-confined semiconductor nanoheterostructures (SNHs) that are composed of multiple component materials in rationally designed spatial arrangements are promising light harvesting and Charge Separation materials for solar energy conversion. SNHs can be engineered to exhibit type I, quasi-type II and type II carrier localization, affecting their photophysical properties and photochemical performances. Unlike bulk semiconductor heterostructures, the electron and hole energy levels and spatial distributions in SNHs can be continuously tuned by adjusting the material dimension through the quantum confinement effect, providing additional control of their properties through wavefunction engineering. In this article, we review recent progress in using wavefunction engineering to control the absorption and emission spectra, single and multiple exciton dynamics and Charge transfer properties of SNHs (core/shell QDs and dot-in-rod nanorods) as well as to improve their performance as light harvesting and Charge Separation materials for solar energy conversion.
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ultrafast Charge Separation and recombination dynamics in lead sulfide quantum dot methylene blue complexes probed by electron and hole intraband transitions
Journal of the American Chemical Society, 2011Co-Authors: Ye Yang, William Rodriguezcordoba, Tianquan LianAbstract:Lead salt quantum dots (QDs) have emerged as attractive materials for solar energy conversion because of their broad spectral response, long exciton lifetime, and efficient multiexciton generation. However, Charge Separation dynamics from these QDs remain poorly understood. In this study we investigate Charge Separation and recombination dynamics in PbS–methylene blue (MB+) complexes by femtosecond transient absorption spectroscopy. We show that while the 1S electrons and holes in excited PbS QDs lead to overlapping transient absorption features in the visible and near-IR regions, their intraband absorptions in the mid-IR can be monitored independently to directly follow the Charge Separation and recombination processes. The Charge Separation and recombination rates in PbS-MB+ complexes were found to be (2.7 ± 0.2) × 1012 and (1.1 ± 0.2) × 1011 s–1, respectively. The ultrafast Charge Separation rate suggests the possibility of hot electron injection and multiexciton dissociation from these strongly quantu...
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ultrafast Charge Separation at cds quantum dot rhodamine b molecule interface
Journal of the American Chemical Society, 2007Co-Authors: Abdelaziz Boulesbaa, Abey Issac, Dave Stockwell, Zhuangqun Huang, Jier Huang, Tianquan LianAbstract:Ultrafast dissociation of excitons in CdS quantum dots via electron transfer to adsorbed rhodamine B (RhB) molecules was demonstrated. The rate of electron transfer can be controlled by the number of adsorbates attached on the nanoparticle and transfer time as fast as 12 picoseconds was observed. The rapid and controllable Charge Separation in this model quantum dot−adsorbate complex provides a potential approach for separating multiple excitons before the exciton−exciton annihilation process.
Jochen Feldmann - One of the best experts on this subject based on the ideXlab platform.
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Charge Separation in type ii tunneling multilayered structures of cdte and cdse nanocrystals directly proven by surface photovoltage spectroscopy
Journal of the American Chemical Society, 2010Co-Authors: Dieter Gross, Ivan Morasero, Thomas Dittrich, Abdelhak Belaidi, C Mauser, Arjan J Houtepen, Enrico Da Como, Andrey L Rogach, Jochen FeldmannAbstract:Charge Separation and diffusion in type II multilayered structures of CdTe and CdSe nanocrystals with a polymer spacer are unambiguously proven by surface photovoltage spectroscopy. Holes accumulate in CdTe nanocrystal layers, and the electrons in CdSe nanocrystal layers. An increase of thickness of the polymer spacer strongly decreases the Charge Separation efficiency. Surface photovoltage transients demonstrate diffusion of the separated Charges over several layers of the same kind of nanocrystals.
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energy transfer versus Charge Separation in type ii hybrid organic inorganic nanocomposites
Nano Letters, 2009Co-Authors: Andrey A Lutich, Andrey L Rogach, Guoxin Jiang, Andrei S Susha, Fernando D Stefani, Jochen FeldmannAbstract:Hybrid organic-inorganic nanomaterials have the potential of providing synergetic properties. Blends of semiconductor nanocrystals and conjugated polymers in particular promise novel optoelectronic properties. Effective design of tailored optoelectronic properties requires a deep understanding of the photophysics of these composite materials, which includes Charge Separation and Dexter and Forster energy transfer. We performed a detailed and quantitative spectroscopic investigation of a type II aligned hybrid system consisting of a blue emitting conducting polymer and CdTe nanocrystals. Although Charge Separation is expected from the type II alignment, we find a dominant (70% efficiency) energy transfer process. We discuss all possible de-excitation pathways for the excitons in terms of the alignment of energy levels, time scales, and physical geometry of the system. This allows us to conclude that energy transfer occurs via the Forster mechanism and provides a clear guideline for the design of novel hybrid materials.
Fengtao Fan - One of the best experts on this subject based on the ideXlab platform.
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internal field enhanced Charge Separation in a single domain ferroelectric pbtio3 photocatalyst
Advanced Materials, 2020Co-Authors: Yong Liu, Huichen Xie, Jian Zhu, Quan Shi, Ruotian Chen, Yuying Gao, Wei Nie, Huanwang Jing, Fengtao FanAbstract:Ferroelectric materials with spontaneous polarization-induced internal electric fields have drawn increasing attention in solar fuel production due to the intrinsic polarized structure. However, the origination of Charge Separation in these materials at the nano/microlevel is ambiguous owing to the complexity of the multielectric fields. Besides, the observed Charge Separation ability is far from theoretical expectation. Herein, by spatially resolved surface photovoltage spectroscopy, it is clearly demonstrated that the depolarization field in single-domain ferroelectric PbTiO3 (PTO) nanoplates is the main driving force for Charge Separation and it can effectively drive photogenerated electrons and holes to the positive and negative polarization facets, respectively. Moreover, the Charge Separation ability of PTO nanoplates increases with increasing particle size along the polarization direction, due to the increasing potential difference between the opposite polarization facets. Furthermore, this driving force for Charge Separation directly contributes to the enhancement of the photocatalytic hydrogen evolution reaction activity in ferroelectrics. Finally, it is proved that the screening field compensates part of the depolarization field and can be diminished by adding a dielectric layer on the ferroelectric surface. These findings demonstrate the importance of increasing the depolarization field and decreasing the screening field for efficient Charge Separation in ferroelectric semiconductor photocatalysts.
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surface polarity induced spatial Charge Separation boosts photocatalytic overall water splitting on gan nanorod arrays
Angewandte Chemie, 2020Co-Authors: Liang Zhang, Yong Liu, Yuying Gao, Fengtao Fan, Chenyi Shao, Junxi Wang, Janchang YanAbstract:Photocatalytic overall water splitting has been recognized as a promising approach to convert solar energy into hydrogen. However, most of the photocatalysts suffer from low efficiencies mainly because of poor Charge Separation. Herein, taking a model semiconductor gallium nitride (GaN) as an example, we uncovered that photogenerated electrons and holes can be spatially separated to the nonpolar and polar surfaces of GaN nanorod arrays, which is presumably ascribed to the different surface band bending induced by the surface polarity. The photogenerated Charge Separation efficiency of GaN can be enhanced significantly from about 8 % to more than 80 % via co-exposing polar and nonpolar surfaces. Furthermore, spatially assembling reduction and oxidation cocatalysts on the nonpolar and polar surfaces remarkably boosts photocatalytic overall water splitting, with the quantum efficiency increased from 0.9 % for the film photocatalyst to 6.9 % for the nanorod arrays photocatalyst.
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the property of surface heterojunction performed by crystal facets for photogenerated Charge Separation
Computational Materials Science, 2018Co-Authors: Zhengde Wei, Yi Zhao, Fengtao FanAbstract:Abstract Crystal facet engineering of semiconductors has been demonstrated to be an important strategy to promote the Separation of photogenerated electron-hole pair for photocatalytic activity, but the mechanism behind is still in debate. Here, density functional theory calculations are used to reveal the detailed property of surface heterojunction, one of popular concepts for Charge Separation, with three typical model systems of TiO2, Cu2WS4 and SrTiO3. The results demonstrate that the conduction band minima and valence band maxima among different facets indeed result in surface heterojunction, thermal-kinetically favorable for spatial Charge Separation. However, these surface heterojunctions, caused by the surface dangling bonds and the interaction between surface atoms, are only in few surface layers (about 1 nm) and may not be powerful enough to initiate the preferential flow of Charges, and the other possible mechanism for Charge Separation should be additionally considered.
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Charge Separation via asymmetric illumination in photocatalytic cu 2 o particles
Nature Energy, 2018Co-Authors: Jian Zhu, Ruotian Chen, Yuying Gao, Shan Pang, Fengtao FanAbstract:Solar-driven photocatalytic reactions provide a potential route to sustainable fuels. These processes rely on the effective Separation of photogenerated Charges, and therefore understanding and exploring the driving force for Charge Separation is key to improving the photocatalytic performance. Here, using surface photovoltage microscopy, we demonstrate that the photogenerated Charges can be separated effectively in a high-symmetry Cu2O photocatalyst particle by asymmetric light irradiation. The holes and electrons are transferred to the illuminated and shadow regions, respectively, of a single photocatalytic particle. Quantitative results show that the intrinsic difference between electron and hole mobilities enables a diffusion-controlled Charge Separation process, which is stronger than that caused by conventional built-in electric fields (40 mV versus 10 mV). Based on the findings, we assemble spatially separated redox co-catalysts on a single photocatalytic particle and, in doing so, enhance the performance for a model photocatalytic reaction by 300%. These findings highlight the driving force caused by Charge mobility differences and the use of asymmetric light illumination for Charge Separation in photocatalysis. Photocatalysts use light to drive chemical reactions; the effective spatial Separation of photogenerated Charges is key to their performance in solar energy conversion. Here, using surface photovoltage microscopy, the authors show that Charges can be separated in photocatalytic particles by asymmetric light irradiation.
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directly probing Charge Separation at interface of tio2 phase junction
Journal of Physical Chemistry Letters, 2017Co-Authors: Yuying Gao, Jian Zhu, Ruotian Chen, Pengli Yan, Baokun Huang, Fengtao FanAbstract:Phase junction is often recognized as an effective strategy to achieve efficient Charge Separation in photocatalysis and photochemistry. As a crucial factor to determine the photogenerated Charges dynamics, there is an increasingly hot debate about the energy band alignment across the interface of phase junction. Herein, we reported the direct measurement of the surface potential profile over the interface of TiO2 phase junction. A built-in electric field up to 1 kV/cm from rutile to anatase nanoparticle was detected by Kelvin Probe Force Microscopy (KPFM). Home-built spatially resolved surface photovoltage spectroscopy (SRSPS) supplies a direct evidence for the vectorial Charge transfer of photogenerated electrons from rutile to anatase. Moreover, the tunable anatase nanoparticle sizes in TiO2 phase junction leads to high surface photovoltage (SPV) by creating completely depleted space Charge region (SCR) and enhancing the Charge Separation efficiency. The results provide a strong basis for understanding...