Article
Materials Science, Multidisciplinary
Peter A. Schultz, Harold P. Hjalmarson
Summary: The E3 transition in irradiated GaAs has been observed to have three distinct components in deep level transient spectroscopy (DLTS). The component designated E3c is found to be metastable, reversible bleaching under minority carrier injection, with an introduction rate depending on Si doping density. First-principles modeling reveals that E3c must be the intimate Sivacancy pair, best described as a Si sitting in a divacancy Sivv. The bleached metastable state is enabled by a doubly site-shifting mechanism, where the defect undergoes a second site shift upon recharging rather than returning to its original E3c-active configuration by reversing the first site shift. Identifying this defect provides insights into short-time annealing kinetics in irradiated GaAs.
Article
Chemistry, Multidisciplinary
Zilong Wu, Yuhan Zhu, Feng Wang, Chuyun Ding, Yanrong Wang, Xueying Zhan, Jun He, Zhenxing Wang
Summary: By constructing vertical metal-semiconductor-metal structures and setting them into a low-resistance state, we successfully reduce the contact resistance of two-dimensional semiconductors and improve their current density. This strategy is applicable to various two-dimensional semiconductors and contact metals, demonstrating good stability and wide application potential.
Article
Multidisciplinary Sciences
Viacheslav Sorkin, Hangbo Zhou, Zhi Gen Yu, Kah-Wee Ang, Yong-Wei Zhang
Summary: In this study, the effects of different types, locations, and densities of point defects in monolayer MoS2 on the electronic structures and Schottky barrier heights (SBH) of Au/MoS2 heterojunction are investigated using DFT calculations. The results show that the SBH of monolayer MoS2 with defects is universally higher than that of the defect-free counterpart. Specifically, S divacancy and Mo-S antisite defects have a larger effect on increasing the SBH compared to S monovacancy. Defects located in the inner sublayer of MoS2 also have a larger impact on the SBH than those in the outer sublayer. Increasing defect density leads to a higher SBH. These findings provide practical guidelines for controlling and optimizing the SBH in Au/MoS2 heterojunctions through defect engineering.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Physical
Wei Li, Alexey V. Akimov
Summary: For simulations using the repetition approximation, the state transition time scales may strongly depend on the length of the repeated data, and the repetition approach could under-or overestimate the time scales by a factor of <= 7-8. This dependence is not directly related to the dispersion of energy gap and nonadiabatic coupling frequencies, but may be influenced by the magnitude of the nonadiabatic couplings.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Felipe Crasto de Lima, Adalberto Fazzio
Summary: Vacancies play a crucial role in the topological transition of transition metal dichalcogenides, inducing a topologically nontrivial phase. Vacancy states in PtSe2 result in a large topological gap within the pristine system gap, allowing the construction of backscattering protected metallic channels embedded in a semiconducting host.
Article
Chemistry, Physical
Ritabrata Sarkar, Md Habib, Sougata Pal
Summary: This study investigates the charge recombination mechanism in macromolecular porphyrin nanorings and finds that the mode of the linker in the nanoring strongly affects charge recombination. The all-butadiyne-linkage inhibits carrier relaxation while the partially fused nanoring expedites quantum transitions. The larger optical gap in the all-butadiyne-linkage nanoring reduces nonadiabatic coupling, resulting in a longer carrier lifetime. Intense phonon peaks and rapid coherence loss also contribute to the prolonged carrier lifetime.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Physical
Hongliang Li, Meng Guo, Zhaohui Zhou, Run Long, Wei-Hai Fang
Summary: Experiments have shown that the lifetime of photoexcited carriers in alpha-Fe2O3 is significantly dependent on the excitation wavelength, but the underlying physical mechanism remains unresolved. In this study, we used nonadiabatic molecular dynamics simulation based on a well-described electronic structure of Fe2O3 to rationalize the puzzling excitation-wavelength dependence of the carrier dynamics. We found that electrons with lower-energy excitation relax fast in the conduction band, while those with higher-energy excitation undergo a slower interband relaxation before a faster intraband relaxation. This study provides insights into the excitation-wavelength dependence of carrier lifetime in Fe2O3, and offers a reference for regulating carrier dynamics in transition-metal oxides through light excitation wavelength.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Review
Chemistry, Multidisciplinary
Xin Wang, Jing Wu, Yuwei Zhang, Yu Sun, Kaikai Ma, Yong Xie, Wenhao Zheng, Zhen Tian, Zhuo Kang, Yue Zhang
Summary: Vacancy defect engineering has been widely used to shape the physicochemical properties of diverse catalysts. This review provides a comprehensive understanding of vacancy engineering in 2D TMDs-based electrocatalysis, covering its background, manufacturing, characterization, and application in the hydrogen evolution reaction. The review also explores the correlations between specific vacancy regulation routes and catalytic performance improvement, and discusses the future prospects of vacancy engineering in advanced defect catalysts.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Teng Wang, Bo Xu, You Wang, Jiaqi Lei, Wenjing Qin, Ke Gui, Chuying Ouyang, Kai-Jie Chen, Hongxia Wang
Summary: This study presents a simple method to enhance energy storage properties by in-situ transformation of nickel cobalt oxide nanowire arrays into hierarchical nanowire-nanosheet arrays. The modified electrode exhibits higher specific capacity, rate capability, and cycling stability in alkaline electrolyte, which is crucial for advanced energy storage devices.
CHINESE CHEMICAL LETTERS
(2022)
Article
Materials Science, Ceramics
Yongxia Li, Binsheng Yang, Bin Liu
Summary: Efficient visible-light-driven photocatalysts face challenges due to high charge recombination rates. The development of BiVO4 nanoparticles with controllable oxygen vacancy levels has shown a significant increase in photocatalytic efficiency, with the optimal oxygen vacancy level leading to a 38% improvement over pure BiVO4. Characterizations revealed that this increase was mainly due to the suppression of electron/hole recombination.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Multidisciplinary
Abinash Kumar, Konstantin Klyukin, Shuai Ning, Cigdem Ozsoy-Keskinbora, Mikhail Ovsyanko, Felix van Uden, Ruud Krijnen, Bilge Yildiz, Caroline A. Ross, James M. LeBeau
Summary: YFeO3 thin films exhibit changes in antiphase boundaries under the influence of Y-Fe antisite defects and strain, displaying polar and bistable characteristics. Density functional theory demonstrates that the presence of Fe-Y antisites significantly decreases the switching barrier.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Physical
Trung T. Pham, Roshan Castelino, Alexandre Felten, Robert Sporken
Summary: In this paper, we report the successful synthesis of single phase 2H-MoTe2 compound on graphene-terminated 6H-SiC(0001) substrate and the effective recovery of its clean surface after exposure to air. The films are analyzed in detail using reflection high energy electron diffraction, X-ray photoemission spectroscopy, and scanning tunneling microscopy.
SURFACES AND INTERFACES
(2022)
Article
Nanoscience & Nanotechnology
Andrew C. Lang, D. Scott Katzer, Neeraj Nepal, David J. Meyer, Rhonda M. Stroud
Summary: Epitaxial transition metal nitrides (TMNs) are a new class of crystalline thin film metals that can be integrated with common group III-nitride semiconductors. This study used high-resolution transmission electron microscopy to identify different phases of tantalum nitrides with N-sublattice ordering, revealing Ta-deficient films with specific planar defects. These findings lay the foundation for the application of this epitaxial TMN material in new electronic and superconducting device structures.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Review
Chemistry, Multidisciplinary
Ruichun Luo, Meng Gao, Chunwen Wang, Juntong Zhu, Roger Guzman, Wu Zhou
Summary: This review provides an overview of the static and in situ investigation of functional structures, defects, and interfaces in 2D transition metal dichalcogenides (TMDs), primarily utilizing scanning transmission electron microscopy and electron energy loss spectroscopy. Recent advancements in in situ visualization and manipulation of 2D TMDs using electron beams are also highlighted.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Physical
Bipeng Wang, Weibin Chu, Alexandre Tkatchenko, Oleg Prezhdo
Summary: The study developed a methodology for nonadiabatic molecular dynamics that utilizes machine learning to reduce the expensive calculations of nonadiabatic couplings and excited state energies, resulting in significant computational savings and improved efficiency.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Review
Chemistry, Multidisciplinary
Zhihao Zhang, Lu Qiao, Ke Meng, Run Long, Gang Chen, Peng Gao
Summary: Lead halide perovskite solar cells have achieved significant progress in efficiency and stability. This review discusses various passivation strategies to address the challenges of defects, charge recombination, and stability in perovskite materials. The article also highlights the need for advanced characterization techniques to understand the mechanisms behind the passivation strategies, and proposes future research directions.
CHEMICAL SOCIETY REVIEWS
(2023)
Article
Chemistry, Physical
Hua Wang, Zhaohui Zhou, Run Long, Oleg Prezhdo
Summary: Compared to the bare Fe2O3 (0001) surface, an alpha-Ga2O3 overlayer reduces surface states and suppresses charge recombination, resulting in a cathodic shift in the onset potential for water oxidation.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Ran Shi, Meng Guo, Run Long
Summary: Simulations show that mixing tin and lead in CH3NH3PbI3 can passivate the midgap state created by an interstitial iodine, reduce electron-hole wave functions overlap, and shorten pure-dephasing time. The charge carrier lifetime extends to 3.6 ns due to reduced nonradiative electron-hole recombination, which is longer than other materials. Tin-lead alloying also increases the defect formation energy, effectively enhancing defect tolerance. Overall, this study reveals the factors controlling the enhanced performance of tin-lead mixed perovskite solar cells.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Cheng Cheng, Oleg V. Prezhdo, Run Long, Wei-Hai Fang
Summary: Identifying photolysis and photothermolysis during a photochemical reaction is challenging due to the non-equilibrium and ultrafast nature of the processes. In this study, the authors use advanced ab initio molecular dynamics to investigate the photodissociation of N2O on a TiO2 surface. They establish the detailed mechanism and find that photothermolysis governs the dissociation when N2O- is short-lived, while photolysis becomes dominant as the N2O- resonance lifetime increases. The authors also demonstrate that thermal dissociation of N2O can be achieved by choosing appropriate metal dopants. Overall, this study provides a fundamental understanding of the competition and synergy between photocatalytic and photothermocatalytic dissociation of N2O and has implications for designing high-performance transition-metal oxide catalysts.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Edoardo Mosconi, Asma A. Alothman, Run Long, Waldemar Kaiser, Filippo De Angelis
Summary: Controlling the chemical properties of A-site cations in 2D metal halide perovskites (MHPs) and in 2D/3D assemblies is crucial for stable and efficient optoelectronic devices. This study rationalizes the chemical interactions of different classes of organic cations in 2D MHPs, emphasizing the potential enhancement in stability through hydrogen bonding within the organic framework. This observation may lead to the design of organic cations with stronger intermolecular interactions for increased stability in MHP-based devices.
ACS ENERGY LETTERS
(2023)
Article
Chemistry, Physical
Run Long, Ran Shi
Summary: Defects such as metal vacancies deteriorate the photoelectric properties of metal halide perovskites. Alkali metal dopants have been shown to improve the performance of mixed tin-lead perovskites. Tin vacancies produce iodine trimers and cause rapid electron-hole recombination, but alkali metal additives eliminate trap states and decelerate charge recombination, enhancing the defect tolerance of tin-lead mixed perovskites.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Lin Zhang, Hengwei Qiu, Ran Shi, Jinsong Liu, Guangliu Ran, Wenkai Zhang, Genban Sun, Run Long, Weihai Fang
Summary: This work reports the attractive performance of perovskite photoconductors based on epitaxial CsPbBr3-Pb4S3Br2 Janus nanocrystals, as well as the carrier relaxation and transfer mechanism of the heterojunction. By combining transient optical absorption and quantum dynamics simulation, it is demonstrated that the photogenerated holes on CsPbBr3 can be successfully extracted by Pb4S3Br2, with hole transfer proceeding about three times faster than energy loss and remaining hot for about 300 fs. This feature favors long-range charge separation and transport, resulting in exceptional responsivity (34.0 A W-1) and specific detectivity (1.26 x 1014 Jones) of the Janus nanocrystal photoconductors.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Hongliang Li, Meng Guo, Zhaohui Zhou, Run Long, Wei-Hai Fang
Summary: Experiments have shown that the lifetime of photoexcited carriers in alpha-Fe2O3 is significantly dependent on the excitation wavelength, but the underlying physical mechanism remains unresolved. In this study, we used nonadiabatic molecular dynamics simulation based on a well-described electronic structure of Fe2O3 to rationalize the puzzling excitation-wavelength dependence of the carrier dynamics. We found that electrons with lower-energy excitation relax fast in the conduction band, while those with higher-energy excitation undergo a slower interband relaxation before a faster intraband relaxation. This study provides insights into the excitation-wavelength dependence of carrier lifetime in Fe2O3, and offers a reference for regulating carrier dynamics in transition-metal oxides through light excitation wavelength.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Ran Shi, Run Long, Wei-Hai Fang, Oleg V. Prezhdo
Summary: By doping complementary cations into 2D layered metal halide perovskites, spontaneous charge separation can be accelerated and charge recombination can be slowed down, resulting in improved photovoltaic performance. Using ab initio nonadiabatic molecular dynamics combined with time-dependent density functional theory, it was found that cesium doping broadens the bandgap and breaks structural symmetry, leading to accelerated charge separation and increased charge carrier lifetime. These findings provide guidelines for future material discovery and perovskite solar cell design.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Hengwei Qiu, Fu Li, Shan He, Ran Shi, Yaoyao Han, Hannikezi Abudukeremu, Lin Zhang, Yan Zhang, Song Wang, Wangyu Liu, Chao Ma, Honghua Fang, Run Long, Kaifeng Wu, Hao Zhang, Jinghong Li
Summary: This study reports the synthesis of uniform, epitaxially grown CsPbBr3/CdS Janus nanocrystal heterostructures with ultrafast charge separation across the electronically coupled interface. Each Janus nanocrystal contains a CdS domain that grows exclusively on a single {220} facet of CsPbBr3 nanocrystals. The promoted charge separation and extraction in epitaxial Janus nanocrystals leads to photoconductors with drastically improved responsivity and detectivity, which is promising for ultrasensitive photodetection.
Article
Engineering, Electrical & Electronic
Yong Lei, Run Long, Hong Li, Chenling Xiong, Chao Yang, Chenghuai Wu, Zhenxuan Yang, Fuling Tang, Wei Wang
Summary: This study demonstrated a through-wall linear-motor type flux pump for non-contact excitation of high-temperature superconducting magnets. The heating parts of the pump are located outside the cryostat to minimize heat load, and the generated heat is dissipated in the air. By using a cryogenic cooler and an insulation HTS double pancake coil, the injection of direct currents into the closed-loop without current leads was successfully achieved, verifying the feasibility and reliability of the linear-motor type flux pump for HTS magnet excitation.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
Article
Chemistry, Physical
Ran Shi, Run Long
Summary: Defects like metal vacancies degrade the photoelectric properties of metal halide perovskites by serving as nonradiative recombination centers. Nonadiabatic molecular dynamics revealed that alkali metal dopants significantly enhance the performance of mixed tin-lead perovskites. Alkali dopants raise the formation energy of tin vacancies to 1 eV, resulting in decreased defect concentration. Tin vacancies facilitate the doping of alkali metals into perovskites. These vacancies generate iodine trimers that create midgap states and promote rapid electron-hole recombination. Alkali metal additives eliminate trap states, weaken nonadiabatic coupling, and slow down charge recombination with a coefficient of 5.5 compared to defective tin-lead mixed perovskites. Our research provides a theoretical model for alkali metal passivation at the atomic level, enhancing the defect tolerance of tin-lead mixed perovskites and offering valuable insights for optimizing high-performance perovskites.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Lin Zhang, Hengwei Qiu, Ran Shi, Jinsong Liu, Guangliu Ran, Wenkai Zhang, Genban Sun, Run Long, Weihai Fang
Summary: This work presents the attractive device performance of perovskite photoconductors based on epitaxial CsPbBr3-Pb4S3Br2 Janus nanocrystals. The carrier relaxation and transfer mechanism of the heterojunction is also investigated. The study demonstrates that the photogenerated holes on CsPbBr3 can be efficiently extracted by Pb4S3Br2, leading to long-range charge separation and transport, resulting in exceptional responsivity and specific detectivity.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Hua Wang, Zhaohui Zhou, Run Long, Oleg Prezhdo
Summary: In this study, ab initio quantum dynamics simulations were performed to investigate the effect α-Ga2O3 overlayers on charge recombination in Hematite photoanode. The results showed that the overlayers eliminated surface states and suppressed charge recombination, explaining the observed cathodic shift in the onset potential for water oxidation and increasing charge carrier lifetime. This work advances the understanding of the influence of surface passivation on charge recombination dynamics and provides guidance for designing novel α-Fe2O3 photoanodes.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Ran Shi, Meng Guo, Run Long
Summary: Simulations show that mixing tin with lead in CH3NH3PbI3 can passivate the midgap state created by an interstitial iodine through compressive strain and upshifted valence band maximum, reduce electron-hole wave functions overlap, and shorten pure dephasing time through high-frequency phonon modes. The significantly reduced nonradiative recombination leads to an extended charge carrier lifetime of 3.6 ns, which is an order of magnitude longer than the Ii-containing CH3NH3PbI3, over 2.5 times longer than pristine CH3NH3PbI3, and even 1.7 times longer than tin-lead mixed perovskite without I-i defects. Tin-lead alloying also increases the I-i defect formation energy, effectively enhancing defect tolerance. This study reveals the factors controlling the enhanced performance of tin-lead mixed perovskite solar cells.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)