Doping with various impurities is an effective approach to improve the photoelectrochemical properties of TiO2. Here, we explore the effect of oxygen vacancy on geometric and elec- tronic properties of compensated （i...Doping with various impurities is an effective approach to improve the photoelectrochemical properties of TiO2. Here, we explore the effect of oxygen vacancy on geometric and elec- tronic properties of compensated （i.e. V-N and Cr-C） and non-compensated （i.e. V-C and Cr-N） codoped anatase TiO2 by performing extensive density functional theory calculations. Theoretical results show that oxygen vacancy prefers to the neighboring site of metal dopant （i.e. V or Cr atom）. After introduction of oxygen vacancy, the unoccupied impurity bands located within band gap of these codoped TiO2 will be filled with electrons, and the posi- tion of conduction band offset does not change obviously, which result in the reduction of photoinduced carrier recombination and the good performance for hydrogen production via water splitting. Moreover, we find that oxygen vacancy is easily introduced in V-N codoped TiO2 under O-poor condition. These theoretical insights are helpful for designing codoped TiO2 with high photoelectrochemical performance.展开更多
Metal halide perovskite nanostructures have emerged as low-dimensional semiconductors of great significance in many fields such as photovoltaics,photonics,and optoelectronics.Extensive efforts on the controlled synthe...Metal halide perovskite nanostructures have emerged as low-dimensional semiconductors of great significance in many fields such as photovoltaics,photonics,and optoelectronics.Extensive efforts on the controlled synthesis of perovskite nanostructures have been made towards potential device applications.The engineering of their band structures holds great promise in the rational tuning of the electronic and optical properties of perovskite nanostructures,which is one of the keys to achieving efficient and multifunctional optoelectronic devices.In this article,we summarize recent advances in band structure engineering of perovskite nanostructures.A survey of bandgap engineering of nanostructured perovskites is firstly presented from the aspects of dimensionality tailoring,compositional substitution,phase segregation and transition,as well as strain and pressure stimuli.The strategies of electronic doping are then reviewed,including defect-induced self-doping,inorganic or organic molecules-based chemical doping,and modification by metal ions or nanostructures.Based on the bandgap engineering and electronic doping,discussions on engineering energy band alignments in perovskite nanostructures are provided for building high-performance perovskite p-n junctions and heterostructures.At last,we provide our perspectives in engineering band structures of perovskite nanostructures towards future low-energy optoelectronics technologies.展开更多
Artificially constructed van der Waals heterostructures(vdWHs)provide an ideal platform for realizing emerging quantum phenomena in condensed matter physics.Two methods for building vdWHs have been developed:stacking ...Artificially constructed van der Waals heterostructures(vdWHs)provide an ideal platform for realizing emerging quantum phenomena in condensed matter physics.Two methods for building vdWHs have been developed:stacking two-dimensional(2D)materials into a bilayer structure with different lattice constants,or with different orientations.The interlayer coupling stemming from commensurate or incommensurate superlattice pattern plays an important role in vdWHs for modulating the band structures and generating new electronic states.In this article,we review a series of novel quantum states discovered in two model vdWH systems—graphene/hexagonal boron nitride(hBN)hetero-bilayer and twisted bilayer graphene(tBLG),and discuss how the electronic structures are modified by such stacking and twisting.We also provide perspectives for future studies on hetero-bilayer materials,from which an expansion of 2D material phase library is expected.展开更多
Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands.We theoretically investigate the evolution of electronic band structures of kagome lattices...Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands.We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential.It is found that the Dirac points move with applied strain.Furthermore,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction.Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.展开更多
Despite being a promising photoanode material for water splitting,WO_(3) has low conductivity,high onset potential,and sluggish water oxidation kinetics.In this study,we designed Ti-doped WO_(3) nanoplate arrays on fl...Despite being a promising photoanode material for water splitting,WO_(3) has low conductivity,high onset potential,and sluggish water oxidation kinetics.In this study,we designed Ti-doped WO_(3) nanoplate arrays on fluoride-doped tin oxide by a seed-free hydrothermal method,and the effects of doping on the photoelectrochemical performance were investigated.The optimal Ti-doped WO_(3) electrode achieved a photocurrent density of 0.53 mA/cm^(2) at 0.6 V(vs Ag/AgCl),110%higher than that of pure WO_(3) nanoplate arrays.Moreover,a significant cathodic shift in the onset potential was observed after doping.X-ray photoelectron spectroscopy valence band and ultraviolet–visible spectra revealed that the band positions of Ti-doped WO_(3) photoanodes moved upward,yielding a lower onset potential.Furthermore,electrochemical impedance spectroscopy measurements revealed that the conductivities of the WO_(3) photoanodes improved after doping,because of the rapid separation of photo-generated charge carriers.Thus,we report a new design route toward efficient and low-cost photoanodes for photoelectrochemical applications.展开更多
In this work,we studied the electronic band structure of the halogen(F,Cl,and Br)functionalized graphdiynes(GDYs)by using hybrid density functional theory.The results revealed that the bandgap energies of modified GDY...In this work,we studied the electronic band structure of the halogen(F,Cl,and Br)functionalized graphdiynes(GDYs)by using hybrid density functional theory.The results revealed that the bandgap energies of modified GDYs increase as the number of halogen atoms increases.It is also found that the position of the valence band maximum(VBM)is influenced by the electronegativity of halogen atoms.The higher the electronegativity,the deeper the VBM of the GDYs modified by the same number of halogen atoms.Importantly,our results revealed that the bandgap of GDY could be effectively tuned by mixing types of halogen atoms.The new generated conduction band and valence band edges are properly aligned with the oxidation and reduction potentials of water.Further thermodynamic analysis confirms that some models with mixing types of halogen atoms exhibit higher performance of overall photocatalytic water splitting than non-mixing models.This work provides useful insights for designing efficient photocatalysts that can be used for overall water splitting.展开更多
Tunneling heterostructures are emerging as a versatile architecture for photodetection due to their advanced optical sensitivity,tailorable detection band,and wellbalanced photoelectric performances.However,the existi...Tunneling heterostructures are emerging as a versatile architecture for photodetection due to their advanced optical sensitivity,tailorable detection band,and wellbalanced photoelectric performances.However,the existing tunneling heterostructures are mainly operated in the visible wavelengths and have been rarely investigated for the nearinfrared detection.Herein,we report the design and realization of a novel broken-gap tunneling heterostructure by combining WSe2 and Bi2Se3,which is able to realize the simultaneous visible and near-infrared detection because of the complementary bandgaps of WSe2 and Bi2Se3(1.46 and 0.3 e V respectively).Thanks to the realigned band structure,the heterostructure shows an ultralow dark current below picoampere and a high tunneling-dominated photocurrent.The photodetector based on our tunneling heterostructure exhibits a superior specific detectivity of 7.9×1012Jones for a visible incident of 532 nm and 2.2×1010Jones for a 1456 nm nearinfrared illumination.Our study demonstrates a new band structure engineering avenue for the construction of van der Waals tunneling heterostructures for high-performance wide band photodetection.展开更多
On-demand modification of the electronic band structures of high-mobility two-dimensional(2D)materials is of great interest for various applications that require rapid tuning of electrical and optical responses of sol...On-demand modification of the electronic band structures of high-mobility two-dimensional(2D)materials is of great interest for various applications that require rapid tuning of electrical and optical responses of solid-state devices.Although electrically tunable superlattice(SL)potentials have been proposed for band structure engineering of the Dirac electrons in graphene,the ultimate goal of engineering emergent quasiparticle excitations that can hybridize with light has not been achieved.We show that an extreme modulation of one-dimensional(1D)SL potentials in monolayer graphene produces ladder-like electronic energy levels near the Fermi surface,resulting in optical conductivity dominated by intersubband transitions(ISBTs).A specific and experimentally realizable platform comprising hBN-encapsulated graphene on top of a 1D periodic metagate and a second unpatterned gate is shown to produce strongly modulated electrostatic potentials.We find that Dirac electrons with large momenta perpendicular to the modulation direction are waveguided via total internal reflections off the electrostatic potential,resulting in flat subbands with nearly equispaced energy levels.The predicted ultrastrong coupling of surface plasmons to electrically controlled ISBTs is responsible for emergent polaritonic quasiparticles that can be optically probed.Our study opens an avenue for exploring emergent polaritons in 2D materials with gate-tunable electronic band structures.展开更多
Polyimide(PI)has emerged as a promising organic photocatalyst owing to its distinct advantages of high visible-light response,facile synthesis,molecularly tunable donor-acceptor structure,and excellent physicochemical...Polyimide(PI)has emerged as a promising organic photocatalyst owing to its distinct advantages of high visible-light response,facile synthesis,molecularly tunable donor-acceptor structure,and excellent physicochemical stability.However,the synthesis of high-quality PI photoelectrode remains a challenge,and photoelectrochemical(PEC)water splitting for PI has been less studied.Herein,the synthesis of uniform PI photoelectrode films via a simple spin-coating method was reported,and their PEC properties were investigated using melamine as donor and various anhydrides as acceptors.The influence of the conjugate size of aromatic unit(phenyl,biphenyl,naphthalene,perylene)of electron acceptor on PEC performance were studied,where naphthalene-based PI photoelectrode exhibited the highest photocurrent response.This is resulted from the unification of widerange light absorption,efficient charge separation and transport,and strong photooxidation capacity.This paper expands the material library of polymer films for PEC applications and contributes to the rational design of efficient polymer photoelectrodes.展开更多
Non-hermiticity presents a vast newly opened territory that harbors new physics and applications such as lasing and sensing.However,only non-Hermitian systems with real eigenenergies are stable,and great efforts have ...Non-hermiticity presents a vast newly opened territory that harbors new physics and applications such as lasing and sensing.However,only non-Hermitian systems with real eigenenergies are stable,and great efforts have been devoted in designing them through enforcing parity-time(PT)symmetry.In this work,we exploit a lesser-known dynamical mechanism for enforcing real-spectra,and develop a comprehensive and versatile approach for designing new classes of parent Hamiltonians with real spectra.Our design approach is based on a new electrostatics analogy for modifed non-Hermitian bulk-boundary correspondence,where electrostatic charge corresponds to density of states and electric felds correspond to complex spectral fow.As such,Hamiltonians of any desired spectra and state localization profle can be reverse-engineered,particularly those without any guiding symmetry principles.By recasting the diagonalization of non-Hermitian Hamiltonians as a Poisson boundary value problem,our electrostatics analogy also transcends the gain/loss-induced compounding of foating-point errors in traditional numerical methods,thereby allowing access to far larger system sizes.展开更多
基金This work was supported by the National Natural Sci- ence Foundation of China （No.11034006, No.21273208, and No.21473168）, the Anhui Provincial Natural Sci- ence Foundation （No.1408085QB26）, the hmdamental Research Funds for the Central Universities, the China Postdoctoral Science Foundation （No.2012M511409）, and the Supercomputing Center of Chinese Academy of Sciences, Shanghai and USTC Supercomputer Cen- ters.
文摘Doping with various impurities is an effective approach to improve the photoelectrochemical properties of TiO2. Here, we explore the effect of oxygen vacancy on geometric and elec- tronic properties of compensated （i.e. V-N and Cr-C） and non-compensated （i.e. V-C and Cr-N） codoped anatase TiO2 by performing extensive density functional theory calculations. Theoretical results show that oxygen vacancy prefers to the neighboring site of metal dopant （i.e. V or Cr atom）. After introduction of oxygen vacancy, the unoccupied impurity bands located within band gap of these codoped TiO2 will be filled with electrons, and the posi- tion of conduction band offset does not change obviously, which result in the reduction of photoinduced carrier recombination and the good performance for hydrogen production via water splitting. Moreover, we find that oxygen vacancy is easily introduced in V-N codoped TiO2 under O-poor condition. These theoretical insights are helpful for designing codoped TiO2 with high photoelectrochemical performance.
基金support from Australian Research Council (ARC, FT150100450, IH150100006 and CE170100039)support from the MCATM and the FLEET+1 种基金the support from Shenzhen Nanshan District Pilotage Team Program (LHTD20170006)support from Guangzhou Science and Technology Program (Grant No. 201804010322)
文摘Metal halide perovskite nanostructures have emerged as low-dimensional semiconductors of great significance in many fields such as photovoltaics,photonics,and optoelectronics.Extensive efforts on the controlled synthesis of perovskite nanostructures have been made towards potential device applications.The engineering of their band structures holds great promise in the rational tuning of the electronic and optical properties of perovskite nanostructures,which is one of the keys to achieving efficient and multifunctional optoelectronic devices.In this article,we summarize recent advances in band structure engineering of perovskite nanostructures.A survey of bandgap engineering of nanostructured perovskites is firstly presented from the aspects of dimensionality tailoring,compositional substitution,phase segregation and transition,as well as strain and pressure stimuli.The strategies of electronic doping are then reviewed,including defect-induced self-doping,inorganic or organic molecules-based chemical doping,and modification by metal ions or nanostructures.Based on the bandgap engineering and electronic doping,discussions on engineering energy band alignments in perovskite nanostructures are provided for building high-performance perovskite p-n junctions and heterostructures.At last,we provide our perspectives in engineering band structures of perovskite nanostructures towards future low-energy optoelectronics technologies.
基金support from the National Natural Science Foundation of China(Grant No.11725418)the National Key Research and Development Program of China(Grant No.2016YFA0301004)+3 种基金Science Challenge Project,China(Grant No.TZ2016004)Beijing Advanced Innovation Center for Future Chip(ICFC)Tsinghua University Initiative Scientific Research Programfunded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)–TRR 173–268565370(projects A02)。
文摘Artificially constructed van der Waals heterostructures(vdWHs)provide an ideal platform for realizing emerging quantum phenomena in condensed matter physics.Two methods for building vdWHs have been developed:stacking two-dimensional(2D)materials into a bilayer structure with different lattice constants,or with different orientations.The interlayer coupling stemming from commensurate or incommensurate superlattice pattern plays an important role in vdWHs for modulating the band structures and generating new electronic states.In this article,we review a series of novel quantum states discovered in two model vdWH systems—graphene/hexagonal boron nitride(hBN)hetero-bilayer and twisted bilayer graphene(tBLG),and discuss how the electronic structures are modified by such stacking and twisting.We also provide perspectives for future studies on hetero-bilayer materials,from which an expansion of 2D material phase library is expected.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11904261 and 11904259).
文摘Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands.We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential.It is found that the Dirac points move with applied strain.Furthermore,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction.Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.
基金Project(Qian Jiao He KY Zi [2021]257) supported provided by the Natural Science Research Project of Education Department of Guizhou Province,ChinaProject(GZSQCC2019003) supported by the High-level Innovative Talent Cultivation Project of Guizhou Province,ChinaProjects(GZLGXM-01,GZLGXM-08) supported by the Academic New Seedling Cultivation and Innovation Exploration Project of Guizhou Institute of Technology,China。
文摘Despite being a promising photoanode material for water splitting,WO_(3) has low conductivity,high onset potential,and sluggish water oxidation kinetics.In this study,we designed Ti-doped WO_(3) nanoplate arrays on fluoride-doped tin oxide by a seed-free hydrothermal method,and the effects of doping on the photoelectrochemical performance were investigated.The optimal Ti-doped WO_(3) electrode achieved a photocurrent density of 0.53 mA/cm^(2) at 0.6 V(vs Ag/AgCl),110%higher than that of pure WO_(3) nanoplate arrays.Moreover,a significant cathodic shift in the onset potential was observed after doping.X-ray photoelectron spectroscopy valence band and ultraviolet–visible spectra revealed that the band positions of Ti-doped WO_(3) photoanodes moved upward,yielding a lower onset potential.Furthermore,electrochemical impedance spectroscopy measurements revealed that the conductivities of the WO_(3) photoanodes improved after doping,because of the rapid separation of photo-generated charge carriers.Thus,we report a new design route toward efficient and low-cost photoanodes for photoelectrochemical applications.
基金funded by the National Natural Science Foundation of China(No.21973013 and No.21673040)the Natural Science Foundation of Fujian Province of China(No.2020J02025)“Chuying Program”for the Top Young Talents of Fujian Province。
文摘In this work,we studied the electronic band structure of the halogen(F,Cl,and Br)functionalized graphdiynes(GDYs)by using hybrid density functional theory.The results revealed that the bandgap energies of modified GDYs increase as the number of halogen atoms increases.It is also found that the position of the valence band maximum(VBM)is influenced by the electronegativity of halogen atoms.The higher the electronegativity,the deeper the VBM of the GDYs modified by the same number of halogen atoms.Importantly,our results revealed that the bandgap of GDY could be effectively tuned by mixing types of halogen atoms.The new generated conduction band and valence band edges are properly aligned with the oxidation and reduction potentials of water.Further thermodynamic analysis confirms that some models with mixing types of halogen atoms exhibit higher performance of overall photocatalytic water splitting than non-mixing models.This work provides useful insights for designing efficient photocatalysts that can be used for overall water splitting.
基金supported by the National Nature Science Foundation of China(21825103 and 51727809)Hubei Provincial Natural Science Foundation of China(2019CFA002)the Fundamental Research Funds for the Central Universities(2019kfyXMBZ018)。
文摘Tunneling heterostructures are emerging as a versatile architecture for photodetection due to their advanced optical sensitivity,tailorable detection band,and wellbalanced photoelectric performances.However,the existing tunneling heterostructures are mainly operated in the visible wavelengths and have been rarely investigated for the nearinfrared detection.Herein,we report the design and realization of a novel broken-gap tunneling heterostructure by combining WSe2 and Bi2Se3,which is able to realize the simultaneous visible and near-infrared detection because of the complementary bandgaps of WSe2 and Bi2Se3(1.46 and 0.3 e V respectively).Thanks to the realigned band structure,the heterostructure shows an ultralow dark current below picoampere and a high tunneling-dominated photocurrent.The photodetector based on our tunneling heterostructure exhibits a superior specific detectivity of 7.9×1012Jones for a visible incident of 532 nm and 2.2×1010Jones for a 1456 nm nearinfrared illumination.Our study demonstrates a new band structure engineering avenue for the construction of van der Waals tunneling heterostructures for high-performance wide band photodetection.
基金supported by the Office of Naval Research (Grant No. N00014-21-1-2056)the Army Research Office (Grant No. W911NF-21-1-0180)+1 种基金the National Science Foundation MRSEC program (Grant No. DMR-1719875)supported in part by the Kwanjeong Fellowship from Kwanjeong Educational Foundation
文摘On-demand modification of the electronic band structures of high-mobility two-dimensional(2D)materials is of great interest for various applications that require rapid tuning of electrical and optical responses of solid-state devices.Although electrically tunable superlattice(SL)potentials have been proposed for band structure engineering of the Dirac electrons in graphene,the ultimate goal of engineering emergent quasiparticle excitations that can hybridize with light has not been achieved.We show that an extreme modulation of one-dimensional(1D)SL potentials in monolayer graphene produces ladder-like electronic energy levels near the Fermi surface,resulting in optical conductivity dominated by intersubband transitions(ISBTs).A specific and experimentally realizable platform comprising hBN-encapsulated graphene on top of a 1D periodic metagate and a second unpatterned gate is shown to produce strongly modulated electrostatic potentials.We find that Dirac electrons with large momenta perpendicular to the modulation direction are waveguided via total internal reflections off the electrostatic potential,resulting in flat subbands with nearly equispaced energy levels.The predicted ultrastrong coupling of surface plasmons to electrically controlled ISBTs is responsible for emergent polaritonic quasiparticles that can be optically probed.Our study opens an avenue for exploring emergent polaritons in 2D materials with gate-tunable electronic band structures.
基金supported by the National Natural Science Foundation of China(Grant No.22005048)the Natural Science Foundation of Jiangsu Province(Grant No.BK20200399)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2242023K40008)the State Key Laboratory of Clean Energy Utilization of Zhejiang University(Open Fund Project No.ZJUCEU2022003).
文摘Polyimide(PI)has emerged as a promising organic photocatalyst owing to its distinct advantages of high visible-light response,facile synthesis,molecularly tunable donor-acceptor structure,and excellent physicochemical stability.However,the synthesis of high-quality PI photoelectrode remains a challenge,and photoelectrochemical(PEC)water splitting for PI has been less studied.Herein,the synthesis of uniform PI photoelectrode films via a simple spin-coating method was reported,and their PEC properties were investigated using melamine as donor and various anhydrides as acceptors.The influence of the conjugate size of aromatic unit(phenyl,biphenyl,naphthalene,perylene)of electron acceptor on PEC performance were studied,where naphthalene-based PI photoelectrode exhibited the highest photocurrent response.This is resulted from the unification of widerange light absorption,efficient charge separation and transport,and strong photooxidation capacity.This paper expands the material library of polymer films for PEC applications and contributes to the rational design of efficient polymer photoelectrodes.
基金supported by Singapore’s MOE Tier I grant WBS No.A-800022-00-00。
文摘Non-hermiticity presents a vast newly opened territory that harbors new physics and applications such as lasing and sensing.However,only non-Hermitian systems with real eigenenergies are stable,and great efforts have been devoted in designing them through enforcing parity-time(PT)symmetry.In this work,we exploit a lesser-known dynamical mechanism for enforcing real-spectra,and develop a comprehensive and versatile approach for designing new classes of parent Hamiltonians with real spectra.Our design approach is based on a new electrostatics analogy for modifed non-Hermitian bulk-boundary correspondence,where electrostatic charge corresponds to density of states and electric felds correspond to complex spectral fow.As such,Hamiltonians of any desired spectra and state localization profle can be reverse-engineered,particularly those without any guiding symmetry principles.By recasting the diagonalization of non-Hermitian Hamiltonians as a Poisson boundary value problem,our electrostatics analogy also transcends the gain/loss-induced compounding of foating-point errors in traditional numerical methods,thereby allowing access to far larger system sizes.
