1
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Yang Y, Zhang Y, Fernandez-Alberti S, Long R. Resolving the Puzzle of Charge Carrier Lifetime in ZnO by Revisiting the Role of Oxygen Vacancy. J Phys Chem Lett 2024; 15:1-8. [PMID: 38126721 DOI: 10.1021/acs.jpclett.3c03195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Zinc oxide (ZnO) is a wide bandgap prototypical n-type semiconductor due to the presence of intrinsic oxygen vacancies (VO). The VO can readily transfer to the most energetically favorable +2 charged VO (VO2+) by losing two electrons mediated by the metastable VO1+ defect. Nevertheless, the influence of charged VO on the charge dynamics in ZnO and the underlying mechanisms remain elusive. By performing nonadiabatic molecular dynamics simulations of the charge trapping and recombination processes, we show that both VO1+ and VO2+ slow down the nonradiative electron-hole recombination via assisted defect states and, thus, extending charge carrier lifetime compared to pristine ZnO. Our study contributes to identifying the different recombination pathways that take place in VO1+ and VO2+ of n-type ZnO systems, providing useful guidance for designing high-performance ZnO-based devices.
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Affiliation(s)
- Yating Yang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
- Department of Radiochemistry, China Institute of Atomic Energy, Beijing 102413, P. R. China
| | - Yitong Zhang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | | | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
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2
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Guo S, Li C, Nie Z, Wang X, Wang M, Tian C, Yan X, Hu K, Long R. Tensile Strain-Dependent Ultrafast Electron Transfer and Relaxation Dynamics in Flexible WSe 2/MoS 2 Heterostructures. J Phys Chem Lett 2023:10920-10929. [PMID: 38033191 DOI: 10.1021/acs.jpclett.3c02943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Understanding and controlling carrier dynamics in two-dimensional (2D) van der Waals heterostructures through strain are crucial for their flexible applications. Here, femtosecond transient absorption spectroscopy is employed to elucidate the interlayer electron transfer and relaxation dynamics under external tensile strains in a WSe2/MoS2 heterostructure. The results show that a modest ∼1% tensile strain can significantly alter the lifetimes of electron transfer and nonradiative electron-hole recombination by >30%. Ab initio non-adiabatic molecular dynamics simulations suggest that tensile strain weakens the electron-phonon coupling, thereby suppressing the transfer and recombination dynamics. Theoretical predictions indicate that strain-induced energy difference increases along the electron transfer path could contribute to the prolongation of the transfer lifetime. A subpicosecond decay process, related to hot-electron cooling, remains almost unaffected by strain. This study demonstrates the potential of tuning interlayer carrier dynamics through external strains, offering insights into flexible optoelectronic device design with 2D materials.
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Affiliation(s)
- Sen Guo
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
- FSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Chaofan Li
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
| | - Zhaogang Nie
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
- FSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Xiaoli Wang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, China
| | - Minghong Wang
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
| | - Cunwei Tian
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
| | - Xinhua Yan
- Nobat Intelligent Equipment (Shandong), Company, Ltd., Liaocheng, Shandong 252000, China
| | - Kaige Hu
- FSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, China
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3
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He J, Long R. Unveiling the Valence State of Interstitial Bromine on Charge Carrier Lifetime in CH 3NH 3PbBr 3 by Quantum Dynamics Simulation. J Phys Chem Lett 2022; 13:4193-4199. [PMID: 35511453 DOI: 10.1021/acs.jpclett.2c00965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Interstitial halogens are detrimental to the optoelectronic properties of metal halide perovskites. Using nonadiabatic (NA) molecular dynamics, we demonstrate that the valence state of interstitial bromine strongly changes the carrier lifetimes of MAPbBr3 (MA = CH3NH3+). Both neutral and negatively charged interstitial bromine create no midgap states, and they decrease the bandgap, weaken the NA coupling, and accelerate decoherence in a different extent with respect to pristine MAPbBr3, making free charge recombination either slow down about a 3-fold or remain largely unchanged. In contrast, a positively charged interstitial bromine forms a Br trimer and introduces a deep electron trap state, causing a 1.4-fold increase of charge recombination followed by a rapid electron trapping or across the bandgap because of an enhanced NA coupling. The simulations uncover the influence of different charged interstitial bromine defects on MAPbBr3 carrier lifetimes and provide rational guidelines for optimizing perovskite solar cells.
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Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
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4
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Zhang S, Deng X, Wu Y, Wang Y, Ke S, Zhang S, Liu K, Lv R, Li Z, Xiong Q, Wang C. Lateral layered semiconductor multijunctions for novel electronic devices. Chem Soc Rev 2022; 51:4000-4022. [PMID: 35477783 DOI: 10.1039/d1cs01092a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Layered semiconductors, represented by transition metal dichalcogenides, have attached extensive attention due to their unique and tunable electrical and optical properties. In particular, lateral layered semiconductor multijunctions, including homojunctions, heterojunctions, hybrid junctions and superlattices, present a totally new degree of freedom in research on electronic devices beyond traditional materials and their structures, providing unique opportunities for the development of new structures and operation principle-based high performance devices. However, the advances in this field are limited by the precise synthesis of high-quality junctions and greatly hampered by ambiguous device performance limits. Herein, we review the recent key breakthroughs in the design, synthesis, electronic structure and property modulation of lateral semiconductor multijunctions and focus on their application-specific devices. Specifically, the synthesis methods based on different principles, such as chemical and external source-induced methods, are introduced stepwise for the controllable fabrication of semiconductor multijunctions as the basics of device application. Subsequently, their structure and property modulation are discussed, including control of their electronic structure, exciton dynamics and optical properties before the fabrication of lateral layered semiconductor multijunction devices. Precise property control will potentially result in outstanding device performances, including high-quality diodes and FETs, scalable logic and analog circuits, highly efficient optoelectronic devices, and unique electrochemical devices. Lastly, we focus on several of the most essential but unresolved debates in this field, such as the true advantages of few-layer vs. monolayer multijunctions, how sharp the interface should be for specific functional devices, and the superiority of lateral multijunctions over vertical multijunctions, highlighting the next-phase strategy to enhance the performance potential of lateral multijunction devices.
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Affiliation(s)
- Simian Zhang
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Xiaonan Deng
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Yifei Wu
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Yuqi Wang
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Shengxian Ke
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Shishu Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Beijing Innovation Center for Future Chips, Tsinghua University, Beijing, 100084, China
| | - Kai Liu
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Ruitao Lv
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Zhengcao Li
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Beijing Innovation Center for Future Chips, Tsinghua University, Beijing, 100084, China.,Frontier Science Center for Quantum Information, Beijing, 100084, China.,Beijing Academy of Quantum Information Sciences, Beijing, 100193, China.
| | - Chen Wang
- State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China.
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5
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Cheng C, Long R. Charge-Compensated Doping Extends Carrier Lifetimes in SrTiO 3 by Passivating Oxygen Vacancy Defects. J Phys Chem Lett 2021; 12:12040-12047. [PMID: 34904842 DOI: 10.1021/acs.jpclett.1c03775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Experiments reported that oxygen vacancies shorten the charge carrier lifetime of SrTiO3 but that it is greatly improved upon Al and Na doping. Using nonadiabatic (NA) molecular dynamics, we demonstrate that the in-gap hole trap state created by an oxygen vacancy can be eliminated by charge-compensated doping when two Ti4+ ions or two Sr2+ ions are equally replaced by Al3+ or Na+ ions. Nevertheless, Al3+ and Na+ reduce the strength of NA coupling to a different extent, resulting in increased charge carrier lifetimes of 4.6 and 1.3 ns. The lifetimes are several times longer than that of the pristine system and 3 orders of magnitude longer than that of defective SrTiO3, which is within 50 ps due to strong NA coupling. The weakly correlated electron and hole wave functions in doped systems accelerate decoherence, further delaying charge recombination. Our study rationalizes the complex charge-phonon dynamics in SrTiO3 and proposes charge-compensated doping for the design of advanced visible-light photocatalysts.
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Affiliation(s)
- Cheng Cheng
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China
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6
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Wang X, Long R. Photoinduced Anomalous Electron Transfer Dynamics at a Lateral MoS 2-Graphene Covalent Junction. J Phys Chem Lett 2021; 12:7553-7559. [PMID: 34351765 DOI: 10.1021/acs.jpclett.1c02169] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Photoinduced charge separation significantly affects the optoelectronic performance of the lateral MoS2-graphene junctions. Generally, an adiabatic mechanism governs electron transfer (ET) at a chemically binding interface. Counterintuitively, we demonstrate, using nonadiabatic (NA) molecular dynamics, that an NA mechanism dominates the ET from MoS2 to graphene in the lateral MoS2-graphene covalent junction. The anomalous ET mechanism arising from the built-in electric field formed at the interface that decreases the donor-acceptor interaction by driving electrons and holes moving to opposite directions. Driven by both graphene and MoS2 vibrations, the photoexcited electrons on MoS2 rapidly transfer into graphene by the NA mechanism within 200 fs, which is faster than electron-phonon energy relaxation and ensures that "hot" electrons can be successfully extracted before they cool and lose energy to heat. The study establishes a mechanistic understanding of the complex charge-phonon dynamics in the lateral MoS2-graphene junctions that are key to optoelectronic and photovoltaic applications.
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Affiliation(s)
- Xiaoli Wang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, P. R. China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, P. R. China
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7
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Yu X, Su Y, Xu WW, Zhao J. Efficient Photoexcited Charge Separation at the Interface of a Novel 0D/2D Heterojunction: A Time-Dependent Ultrafast Dynamic Study. J Phys Chem Lett 2021; 12:2312-2319. [PMID: 33651620 DOI: 10.1021/acs.jpclett.1c00023] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
To achieve efficient conversion and avoid loss of solar energy, ultrafast charge separation and slow electron-hole recombination are desired. Combining time-dependent density functional theory (TD-DFT) with nonadiabatic molecular dynamics, Au9(PH3)8/MoS2, as a prototype for zero-dimensional/two-dimensional (0D/2D) heterojunction, has been demonstrated to present excellent light absorption capacity and effective charge separation characteristics. In the heterojunction, photoexcitation of the Au9(PH3)8 nanocluster drives an ultrafast electron transfer from Au9(PH3)8 to MoS2 within 20 fs, whereas photoexcitation of the MoS2 nanosheet leads to hole transfer from MoS2 to Au9(PH3)8 within 680 fs. The strong nonadiabatic coupling and prominent density overlap are responsible for the faster electron separation relative to hole separation. In competition with the charge separation, electron-hole recombination requires 205 ns, ensuring an effective carrier separation. Our atomistic TD-DFT simulation provides valuable insights into the photocarrier dynamics at the Au9(PH3)8/MoS2 interface, which would stimulate the exploration of 0D/2D hybrid materials for photovoltaic and optoelectronic devices.
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Affiliation(s)
- Xueke Yu
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Yan Su
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024, China
| | - Wen-Wu Xu
- Department of Physics, School of Physical Science and Technology, Ningbo University, Ningbo 315211, China
| | - Jijun Zhao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024, China
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8
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Berweger S, Zhang H, Sahoo PK, Kupp BM, Blackburn JL, Miller EM, Wallis TM, Voronine DV, Kabos P, Nanayakkara SU. Spatially Resolved Persistent Photoconductivity in MoS 2-WS 2 Lateral Heterostructures. ACS NANO 2020; 14:14080-14090. [PMID: 33044054 DOI: 10.1021/acsnano.0c06745] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The optical and electronic properties of 2D semiconductors are intrinsically linked via the strong interactions between optically excited bound species and free carriers. Here we use near-field scanning microwave microscopy (SMM) to image spatial variations in photoconductivity in MoS2-WS2 lateral multijunction heterostructures using photon energy-resolved narrowband illumination. We find that the onset of photoconductivity in individual domains corresponds to the optical absorption onset, confirming that the tightly bound excitons in transition metal dichalcogenides can nonetheless dissociate into free carriers. These photogenerated carriers are most likely n-type and are seen to persist for up to days. Informed by finite element modeling we reveal that they can increase the carrier density by up to 200 times. This persistent photoconductivity appears to be dominated by contributions from the multilayer MoS2 domains, and we attribute the flake-wide response in part to charge transfer across the heterointerface. Spatial correlation of our SMM imaging with photoluminescence (PL) mapping confirms the strong link between PL peak emission photon energy, PL intensity, and the local accumulated charge. This work reveals the spatially and temporally complex optoelectronic response of these systems and cautions that properties measured during or after illumination may not reflect the true dark state of these materials but rather a metastable charged state.
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Affiliation(s)
- Samuel Berweger
- Applied Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Hanyu Zhang
- Materials and Chemical Science and Technology Directorate, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Prasana K Sahoo
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
- Materials Science Centre, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Benjamin M Kupp
- Applied Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, United States
- The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jeffrey L Blackburn
- Materials and Chemical Science and Technology Directorate, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Elisa M Miller
- Materials and Chemical Science and Technology Directorate, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Thomas M Wallis
- Applied Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Dmitri V Voronine
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Pavel Kabos
- Applied Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Sanjini U Nanayakkara
- Materials and Chemical Science and Technology Directorate, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
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9
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Yang Y, Tokina MV, Fang WH, Long R, Prezhdo OV. Influence of tungsten doping on nonradiative electron–hole recombination in monolayer MoSe2 with Se vacancies. J Chem Phys 2020; 153:154701. [DOI: 10.1063/5.0020720] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yating Yang
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Marina V. Tokina
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People’s Republic of China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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10
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He J, Fang WH, Long R, Prezhdo OV. Why Oxygen Increases Carrier Lifetimes but Accelerates Degradation of CH3NH3PbI3 under Light Irradiation: Time-Domain Ab Initio Analysis. J Am Chem Soc 2020; 142:14664-14673. [DOI: 10.1021/jacs.0c06769] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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11
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He J, Fang WH, Long R. Two-Dimensional Perovskite Capping Layer Simultaneously Improves the Charge Carriers' Lifetime and Stability of MAPbI 3 Perovskite: A Time-Domain Ab Initio Study. J Phys Chem Lett 2020; 11:5100-5107. [PMID: 32513007 DOI: 10.1021/acs.jpclett.0c01463] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two- (2D) and three-dimensional (3D) heterostructured perovskites show enhanced stability and an extended charge lifetime compared to those of the 3D component. The mystery remains unexplored for both phenomena in the class of the typical type-I heterojunction. By using time-domain density functional theory combined with nonadiabatic (NA) molecular dynamics simulations for the MA3Bi2I9/MAPbI3 (MA = CH3NH3+) junction, we demonstrate that the formation of I-Pb chemical bonds at the junction suppresses the atomic motions. The inhibited charge recombination in the junction is ascribed to the increased band gap, reduced NA coupling, and shortened coherence time. By localizing the hole wave function, the NA coupling is decreased by about a factor of 1.4. The presence of multiple phonon modes, particularly the Bi-I vibrations, accelerates decoherence about twice as fast as that in the pristine MAPbI3. As a result, the 2D capping layer reduces the recombination in MAPbI3 by more than a factor of 2, decreasing charge and energy losses. The strategy can be applied to optimize the performance of other 2D/3D heterostructured perovskite solar cells.
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Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, P. R. China
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12
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Smith B, Akimov AV. Hot Electron Cooling in Silicon Nanoclusters via Landau-Zener Nonadiabatic Molecular Dynamics: Size Dependence and Role of Surface Termination. J Phys Chem Lett 2020; 11:1456-1465. [PMID: 31958367 DOI: 10.1021/acs.jpclett.9b03687] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We develop a new express methodology for modeling excited-state dynamics occurring in dense manifolds of electronic states in atomistic systems. The approach leverages a modified Landau-Zener formula, the neglect of a back-reaction approximation, and the highly efficient density functional tight-binding method. We study the hot electron dynamics in a series of H- and F-terminated silicon nanocrystals (NCs) containing up to several hundred atoms. We explain the slower electron cooling dynamics in F-terminated NCs by the larger energy gaps between the adjacent electronic states in these systems as well as their slower fluctuations. We conclude that both the mass and chemical identity of the surface termination groups equally influence the electron dynamics, on average. However, the mass effect becomes dominant for higher-energy excitations. We find that the electron decay dynamics in F-terminated NCs has a greater sensitivity to the mass of the surface ligands than do the H-terminated NCs and explain this observation by the details of the electron-phonon coupling in the systems. We find that in the H-terminated NCs, electronic transitions in the cooling process occur predominantly between the surface states, whereas in F-terminated Si NCs, both surface and NC core states are coupled to the nuclear vibrations. We find that electron energy relaxation is accelerated in larger NCs and attribute this effect to the higher densities of states and smaller energy gaps in these systems.
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Affiliation(s)
- Brendan Smith
- Department of Chemistry , University at Buffalo, The State University of New York , Buffalo , New York 14260 , United States
| | - Alexey V Akimov
- Department of Chemistry , University at Buffalo, The State University of New York , Buffalo , New York 14260 , United States
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13
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Smith B, Akimov AV. Modeling nonadiabatic dynamics in condensed matter materials: some recent advances and applications. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:073001. [PMID: 31661681 DOI: 10.1088/1361-648x/ab5246] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This review focuses on recent developments in the field of nonadiabatic molecular dynamics (NA-MD), with particular attention given to condensed-matter systems. NA-MD simulations for small molecular systems can be performed using high-level electronic structure (ES) calculations, methods accounting for the quantization of nuclear motion, and using fewer approximations in the dynamical methodology itself. Modeling condensed-matter systems imposes many limitations on various aspects of NA-MD computations, requiring approximations at various levels of theory-from the ES, to the ways in which the coupling of electrons and nuclei are accounted for. Nonetheless, the approximate treatment of NA-MD in condensed-phase materials has gained a spin lately in many applied studies. A number of advancements of the methodology and computational tools have been undertaken, including general-purpose methods, as well as those tailored to nanoscale and condensed matter systems. This review summarizes such methodological and software developments, puts them into the broader context of existing approaches, and highlights some of the challenges that remain to be solved.
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Affiliation(s)
- Brendan Smith
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, United States of America
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14
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Yang Y, Fang WH, Benderskii A, Long R, Prezhdo OV. Strain Controls Charge Carrier Lifetimes in Monolayer WSe 2: Ab Initio Time Domain Analysis. J Phys Chem Lett 2019; 10:7732-7739. [PMID: 31755714 DOI: 10.1021/acs.jpclett.9b03105] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mono- and few-layer transition metal dichalcogenides (TMDs) are among the most appealing candidates for electronic and optoelectronic devices. During synthesis, TMDs actively interact with substrates, which induce notable strain and influence significantly charge carriers in TMDs. By performing time-domain ab initio simulations on monolayer WSe2, we demonstrate that charge carrier lifetimes vary by a factor of 3 within a typical 1% strain range, the bandgap changes by 0.2 eV, and electron-phonon interactions vary by 60%. Fortuitously, the most common tensile strain extends the lifetimes. The changes arise because of modifications in interatomic interactions. Further, compared to the optimized structure, at ambient temperature the bandgap drops by 0.1 eV and fluctuates by 0.1 eV. WSe2 obeys linear response within 1% strain; however, further strain leads to nonlinear qualitative changes in WSe2 electronic properties. The conduction band is affected more strongly than the valence band. Charges couple to phonons within a 100-400 cm-1 frequency range, with the strongest coupling to in-plane and out-of-plane modes at 250 cm-1. The reported findings agree with the available experiments and should be generic to other 2D materials. The strain effects need to be considered during TMD synthesis and provide means to control and tune TMD properties for 2D device applications.
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Affiliation(s)
- Yating Yang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P.R. China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P.R. China
| | - Alex Benderskii
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P.R. China
| | - Oleg V Prezhdo
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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15
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Smith B, Akimov AV. A comparative analysis of surface hopping acceptance and decoherence algorithms within the neglect of back-reaction approximation. J Chem Phys 2019; 151:124107. [DOI: 10.1063/1.5122770] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Brendan Smith
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA
| | - Alexey V. Akimov
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA
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16
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Qiao L, Long R, Fang WH. Surface Pb-Dimer Passivated by Molecule Oxygen Notably Suppresses Charge Recombination in CsPbBr 3 Perovskites: Time-Domain Ab Initio Analysis. J Phys Chem Lett 2019; 10:5499-5506. [PMID: 31475525 DOI: 10.1021/acs.jpclett.9b02201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Experiments show that excess lead atoms accelerate charge recombination while oxygen passivation can heal the defects and enhance solar cell efficiency. Using ab initio nonadiabatic (NA) molecular dynamics, we demonstrate that an excess lead atom forms a Pb-dimer with a single surface lead atom of CsPbBr3(001) surface and creates a deep hole trap. The electron-hole recombination is accelerated to over 10 ps via fast hole trapping or bypassing the hole trap compared to the pristine CsPbBr3, occurring on tens of picoseconds. Pb-dimer passivated with oxygen molecules forms Pb-O bonds, breaks the Pb-dimer, and removes the trap state, leading to a decrease in the recombination and extending excited-state lifetime to over 100 ps. The deceleration arises mainly due to the reduced NA coupling and short decoherence time. The study advances our understanding of excited-state dynamics of all-inorganic perovskites in the presence of excess lead and oxygen atmosphere.
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Affiliation(s)
- Lu Qiao
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , People's Republic of China
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17
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Wei W, Huang B, Dai Y. Photoexcited charge carrier behaviors in solar energy conversion systems from theoretical simulations. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2019. [DOI: 10.1002/wcms.1441] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Wei Wei
- School of Physics, State Key Laboratory of Crystal Materials Shandong University Jinan China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials Shandong University Jinan China
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials Shandong University Jinan China
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18
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Qin H, Pei QX, Liu Y, Zhang YW. The mechanical and thermal properties of MoS 2-WSe 2 lateral heterostructures. Phys Chem Chem Phys 2019; 21:15845-15853. [PMID: 31282519 DOI: 10.1039/c9cp02499a] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The recently fabricated monolayer MoS2-WSe2 lateral heterostructures are promising for many interesting applications, such as p-n diodes, photodetectors, transistors, sensors, light-emitting diodes and thermoelectric and flexible nanodevices. In this work, we study the mechanical and thermal properties of MoS2-WSe2 lateral heterostructures by using molecular dynamics (MD) simulations based on the recently parameterized Stillinger-Weber (SW) potential. It is found that the fracture strength and fracture strain of MoS2-WSe2 lateral heterostructures are dictated by the mechanical properties of MoS2, and are very sensitive to temperature. However, when a crack is introduced in the MoS2-WSe2 heterostructures, failure may occur either in MoS2 or WSe2, depending on the crack length and location. Interestingly, the fracture strengths obtained from our MD simulations are in agreement with those obtained from the Griffith theory. Our MD simulations further reveal that, in addition to the low thermal conductivities of MoS2 and WSe2, the MoS2-WSe2 heterojunctions exhibit a very low interfacial thermal conductance, which is about one order of magnitude lower than that of graphene-hBN heterojunctions.
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Affiliation(s)
- Huasong Qin
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, China710049 and Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore.
| | - Qing-Xiang Pei
- Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore.
| | - Yilun Liu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, China710049
| | - Yong-Wei Zhang
- Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore.
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19
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Ávalos-Ovando O, Mastrogiuseppe D, Ulloa SE. Lateral heterostructures and one-dimensional interfaces in 2D transition metal dichalcogenides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:213001. [PMID: 30794993 DOI: 10.1088/1361-648x/ab0970] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The growth and exfoliation of two-dimensional (2D) materials have led to the creation of edges and novel interfacial states at the juncture between crystals with different composition or phases. These hybrid heterostructures (HSs) can be built as vertical van der Waals stacks, resulting in a 2D interface, or as stitched adjacent monolayer crystals, resulting in one-dimensional (1D) interfaces. Although most attention has been focused on vertical HSs, increasing theoretical and experimental interest in 1D interfaces is evident. In-plane interfacial states between different 2D materials inherit properties from both crystals, giving rise to robust states with unique 1D non-parabolic dispersion and strong spin-orbit effects. With such unique characteristics, these states provide an exciting platform for realizing 1D physics. Here, we review and discuss advances in 1D heterojunctions, with emphasis on theoretical approaches for describing those between semiconducting transition metal dichalcogenides MX 2 (with M = Mo, W and X = S, Se, Te), and how the interfacial states can be characterized and utilized. We also address how the interfaces depend on edge geometries (such as zigzag and armchair) or strain, as lattice parameters differ across the interface, and how these features affect excitonic/optical response. This review is intended to serve as a resource for promoting theoretical and experimental studies in this rapidly evolving field.
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Affiliation(s)
- O Ávalos-Ovando
- Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, OH 45701-2979, United States of America
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20
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Wang S, Fang WH, Long R. Hydrogen Passivated Silicon Grain Boundaries Greatly Reduce Charge Recombination for Improved Silicon/Perovskite Tandem Solar Cell Performance: Time Domain Ab Initio Analysis. J Phys Chem Lett 2019; 10:2445-2452. [PMID: 31034228 DOI: 10.1021/acs.jpclett.9b00874] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
By performing nonadiabatic molecular dynamics simulations, we demonstrate that grain boundaries (GBs) can induce the indirect-to-direct transition of the silicon band gap. However, missing a silicon atom creates an electron trap state in the GBs. Electron trapping by the silicon vacancy occurs on tens of picoseconds followed by recombination of the trapped electron and valence band hole on sub-100 ps, which operates parallel to recombination of the free electron and hole on a similar time scale. The recombination is greatly accelerated by 2 orders of magnitude compared to the GBs without a silicon vacancy. Hydrogen passivation eliminates the trap state and notably delays the charge recombination due to an increased band gap and a shortened coherence time, extending the excited-state lifetime to sub-10 ns. Our study provides an atomistic description of how charge recombination in the silicon can be efficiently reduced, suggesting a rational route to enhance silicon/perovskite tandem solar cells performance.
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Affiliation(s)
- Siyu Wang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing , 100875 , People's Republic of China
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21
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Wang S, Luo Q, Fang WH, Long R. Interfacial Engineering Determines Band Alignment and Steers Charge Separation and Recombination at an Inorganic Perovskite Quantum Dot/WS 2 Junction: A Time Domain Ab Initio Study. J Phys Chem Lett 2019; 10:1234-1241. [PMID: 30818951 DOI: 10.1021/acs.jpclett.9b00285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Using time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we demonstrate that interfacial interaction between WS2 and CsPbBr3 quantum dots (QDs) determines the band alignment, leading to a type-II and type-I heterojunction for the WS2 contacting with Cs/Br- and PbBr2-terminated facet QD, respectively. In the type-II heterojunction, electron transfer is faster than hole transfer arising due to the stronger NA coupling, higher density of electron acceptor states, and more and higher phonon modes involved. Both the electron and hole transfer times are subpicosecond, in agreement with experiments. The energy lost by the electron and hole is slower than charge transfer by several times, facilitating keeping charge carriers sufficiently "hot". Particularly, the electron-hole recombination occurs over 1 ns, favoring a long-lived charge-separated state. Detailed atomistic insights into the photoinduced charge and energy dynamics at the WS2/QD interface provide valuable guidelines for improving performance of perovskite/transition-metal dichalcogenide solar cells.
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Affiliation(s)
- Siyu Wang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Qiquan Luo
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei 230026 , People's Republic of China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
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22
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He J, Fang WH, Long R, Prezhdo OV. Superoxide/Peroxide Chemistry Extends Charge Carriers’ Lifetime but Undermines Chemical Stability of CH3NH3PbI3 Exposed to Oxygen: Time-Domain ab Initio Analysis. J Am Chem Soc 2019; 141:5798-5807. [DOI: 10.1021/jacs.8b13392] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jinlu He
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, People’s Republic of China
| | - Wei-Hai Fang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, People’s Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing, 100875, People’s Republic of China
| | - Oleg V. Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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23
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Li F, Wei W, Wang H, Huang B, Dai Y, Jacob T. Intrinsic Electric Field-Induced Properties in Janus MoSSe van der Waals Structures. J Phys Chem Lett 2019; 10:559-565. [PMID: 30658531 DOI: 10.1021/acs.jpclett.8b03463] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Focusing on two-dimensional (2D) Janus MoSSe monolayers, we show that simultaneously existing in-plane and out-of-plane intrinsic electric fields cause Zeeman- and Rashba-type spin splitting, respectively. In MoSSe van der Waals (vdW) structures, intrinsic electric field results in a large interlayer band offset. Therefore, large interlayer band offset, being the driving force for interlayer excitons, endows ultralong lifetimes to excitons and might dissociate excitons into free carriers. In comparison to its parent structure (i.e., MoS2), MoSSe vdW structures are rather appealing for new concepts in light-electricity interconversion. In addition, the Rashba effects could be tuned by changing the interlayer distances due to the competition between the intralayer and interlayer electric field. Due to the large band offset, valley polarization relaxation is markedly reduced, promising enhanced valley polarization and ultralong valley lifetimes. As a result, MoSSe vdW structures harbor strong valley-contrasting physics, making them competitive systems to their parent structures.
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Affiliation(s)
- Fengping Li
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Jinan 250100 , China
| | - Wei Wei
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Jinan 250100 , China
| | - Hao Wang
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Jinan 250100 , China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Jinan 250100 , China
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Jinan 250100 , China
| | - Timo Jacob
- Institute of Electrochemistry , Ulm University , Albert-Einstein-Allee 47 , D-89081 Ulm , Germany
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24
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Qiao L, Sun X, Long R. Mixed Cs and FA Cations Slow Electron-Hole Recombination in FAPbI 3 Perovskites by Time-Domain Ab Initio Study: Lattice Contraction versus Octahedral Tilting. J Phys Chem Lett 2019; 10:672-678. [PMID: 30681858 DOI: 10.1021/acs.jpclett.8b03729] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Using time domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we show that electron-hole recombination takes subnanoseconds in FAPbI3, showing excellent agreement with experiment. Cs doping retards charge recombination by factors of 1.1 and 3.1 due to lattice contraction and octahedral tilting, respectively. Lattice contraction decreases the NA coupling and increases the coherence time arising from the suppressed atomic fluctuations, slightly slowing recombination because the two factors have an opposite influence on quantum transition. In contrast, octahedral tilting simultaneously decreases the NA coupling, thanks to the reduced overlap between Pb and I orbitals, and the coherence time, extending the excited-state lifetime over 1 ns. Our simulations provide a mechanistic understanding for delayed charge losses in the mixed Cs and FA system, suggesting a rational strategy to improve perovskite solar cell performance.
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Affiliation(s)
- Lu Qiao
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Xueqin Sun
- School of Environmental and Material Engineering , Yantai University , Yantai 264005 , People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
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25
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Zereshki P, Wei Y, Long R, Zhao H. Layer-Coupled States Facilitate Ultrafast Charge Transfer in a Transition Metal Dichalcogenide Trilayer Heterostructure. J Phys Chem Lett 2018; 9:5970-5978. [PMID: 30257564 DOI: 10.1021/acs.jpclett.8b02622] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Forming van der Waals multilayer structures with two-dimensional materials is a promising new method for material discovery. The weak van der Waals interlayer interaction without atomic correspondence relaxes lattice matching requirement and allows formation of high-quality interfaces with virtually any combination of two-dimensional materials. However, the weak nature of the van der Waals interaction also makes it challenging to harness emergent properties of such multilayer materials. Previous studies have indicated that in transition metal dichalcogenide bilayer heterostructures, the interlayer charge and energy transfer is highly efficient. Therefore, it is important to understand interlayer coupling in these materials and its role on charge and energy transfer. Here we show that in a MoSe2/WSe2/WS2 trilayer, the interlayer coupling is strong enough to form layer-coupled states in the conduction band with the electron wave function extends to all three layers. Density functional theory calculations reveal that the layer-coupled states in Q valley are about 0.1 eV below the individual monolayer states in K valley, which is consistent with photoluminescence measurements. Transient absorption measurements show that these layer-coupled states provide a channel for ultrafast interlayer charge transfer between the top WS2 and the bottom MoSe2 layers. In this process, electrons from the K valley of the individual monolayers are scattered to the layer-coupled states in Q valley. Such a partial charge transfer allows formation of partial-indirect excitons with the holes in one monolayer while electrons shared by three layers. The formation of layer-coupled states is promising for harnessing emergent properties of transition metal dichalcogenide multilayer heterostructures. Our findings also provide new ingredient to understand charge and energy transfer in transition metal dichalcogenide heterobilayers, as the layer-coupled states can play important roles in the efficient transfer observed in these systems.
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Affiliation(s)
- Peymon Zereshki
- Department of Physics and Astronomy , The University of Kansas , Lawrence , Kansas 66045 , United States
| | - Yaqing Wei
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , People's Republic of China
| | - Hui Zhao
- Department of Physics and Astronomy , The University of Kansas , Lawrence , Kansas 66045 , United States
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26
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Zhang R, Zhang L, Zheng Q, Gao P, Zhao J, Yang J. Direct Z-Scheme Water Splitting Photocatalyst Based on Two-Dimensional Van Der Waals Heterostructures. J Phys Chem Lett 2018; 9:5419-5424. [PMID: 30180588 DOI: 10.1021/acs.jpclett.8b02369] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Mimicking the natural photosynthesis in plants, Z-scheme water splitting is a promising strategy to improve photocatalytic activity. Searching for the direct Z-scheme photocatalysts is urgent and the crucial factor for the photocatalytic efficiency is the photogenerated electron-hole ( e-h) recombination rate at the interface of two photosystems. In this report, based on time-dependent ab initio nonadiabatic molecular dynamics (NAMD) investigation, we first report a two-dimensional (2D) metal-free van der Waals (vdW) heterostructure consisting of monolayer BCN and C2N as a promising candidate for direct Z-scheme photocatalysts for water splitting. It is shown that the time scale of e-h recombination of BCN/C2N is within 2 ps. Among such e-h recombination events, more than 85% are through the e-h recombination at the interface. NAMD simulations based on frozen phonon method prove that such an ultrafast interlayer e-h recombination is assisted by intralayer optical phonon modes and the interlayer shear phonon mode induced by vdW interaction. In these crucial phonon modes, the interlayer relative movements which are lacking in traditional heterostructures with strong interactions, yet exist generally in various 2D vdW heterostructures, are significant. Our results prove that the 2D vdW heterostructure family is convincing for a new type of direct Z-scheme photocatalysts searching.
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Affiliation(s)
- Ruiqi Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Lili Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Qijing Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Pengfei Gao
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Jin Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
- Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
- Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Jinlong Yang
- Hefei National Laboratory for Physical Sciences at the Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
- Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
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27
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Wei Y, Long R. Grain Boundaries Are Benign and Suppress Nonradiative Electron-Hole Recombination in Monolayer Black Phosphorus: A Time-Domain Ab Initio Study. J Phys Chem Lett 2018; 9:3856-3862. [PMID: 29952569 DOI: 10.1021/acs.jpclett.8b01654] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Using time-domain density functional theory combined with nonadiabatic molecular dynamics, we demonstrate that both symmetrical (GB_s) and asymmetrical grain boundaries (GB_a) significantly extend charge-carrier lifetime compared with monolayer black phosphorus. Boundaries create no deep trap states, which decrease electron-phonon coupling. As a result, GB_s increases carrier lifetime by a factor of 22, whereas GB_a extends the lifetime by a factor of 4. More importantly, the interplay between the immobile electron localized at the boundaries in the GB_s and extended excited-state lifetime facilitates a chemical reaction, which is beneficial for photocatalysts. In contrast, GB_a separates electron and hole spatially in different locations, which forms a long-lived charge-separated state and is favorable for photovoltaics. Our simulations demonstrate that grain boundaries are benign and retard nonradiative electron-hole recombination in monolayer black phosphorus, suggesting a route to reduce energy losses via rational choice of defect to realize high-performance photovoltaic and photocatalytic devices.
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Affiliation(s)
- Yaqing Wei
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P. R. China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P. R. China
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28
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Murthy AA, Stanev TK, Cain JD, Hao S, LaMountain T, Kim S, Speiser N, Watanabe K, Taniguchi T, Wolverton C, Stern NP, Dravid VP. Intrinsic Transport in 2D Heterostructures Mediated through h-BN Tunneling Contacts. NANO LETTERS 2018; 18:2990-2998. [PMID: 29678116 DOI: 10.1021/acs.nanolett.8b00444] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding the electronic transport of monolayer transition metal dichalcogenides (TMDs) and their heterostructures is complicated by the difficulty in achieving electrical contacts that do not perturb the material. Typically, metal deposition on monolayer TMDs leads to hybridization between the TMD and the metal, which produces Schottky barriers at the metal/semiconductor interface. In this work, we apply the recently reported hexagonal boron nitride (h-BN) tunnel contact scheme to probe the junction characteristics of a lateral TMD heterostructure grown via chemical vapor deposition. We first measure the electronic properties across the junction before elucidating optoelectronic generation mechanisms via scanning photocurrent microscopy. We find that the rectification ratio measured using the encapsulated, tunnel contact scheme is almost 2 orders of magnitude smaller than that observed via conventional metal contact geometry, which implies that the metal/semiconductor Schottky barriers play large roles in this aspect. Furthermore, we find that both the photovoltaic as well as hot carrier generation effects are dominant mechanisms driving photoresponse, depending on the external biasing conditions. This work is the first time that this encapsulation scheme has been applied to lateral heterostructures and serves as a reference for future electronic measurements on this material. It also simultaneously serves as a framework to more accurately assess the electronic transport characteristics of 2D heterostructures and better inform future device architectures.
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Affiliation(s)
| | | | | | | | | | | | | | - Kenji Watanabe
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Takashi Taniguchi
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
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