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64. Zero-Dimensional Halides with ns2Electron (Sb3+) Activation to Generate Broad Photoluminescence

Author

Hou, An, Fan, Liubing, Xiong, Yan, Lin, Jiawei, Liu, Kunjie, Chen, Mingyue, Guo, Zhongnan, Zhao, Jing, and Liu, Quanlin

Abstract

Organic–inorganic metal halides (OIMHs) have various crystal structures and offer excellent semiconducting properties. Here, we report three novel OIMHs, (PPA)6InBr9(PPA = [C6H5(CH2)3NH3]+), (PBA)2SbBr5, and (PBA)2SbI6(PBA = [C6H5(CH2)4NH3]+), showing typical zero-dimensional (0D) structure, octahedra dimers, and corner-sharing one-dimensional chains and crystallized in the monoclinic system with P21, P21/c, and C2/cspace groups, respectively. (PPA)6InBr9, (PBA)2SbBr5, and (PBA)2SbI6have experimental optical band gaps of ∼3.16, ∼2.24, and 1.48 eV, respectively. (PPA)6InBr9exhibits bright-orange light emission centered at 642 nm with a full-width at half-maximum of 179 nm (0.51 eV) and a Stokes shift of 277 nm (1.46 eV). After Sb3+doping, the peak position did not change, and the photoluminescence quantum yield increased significantly from 9.2 to 53.0%. The efficient emission of Sb:(PPA)6InBr9stems from the isolated ns2luminescent center and strong electron–phonon coupling, making the spin-forbidden 3P1–1S0observable. By combining commercial blue and green phosphors with orange-red-light-emitting (PPA)6In0.99Sb0.01Br9, a white-light-emitting diode was constructed, with the color-rendering index reaching up to 92.3. Our work highlights three novel 0D OIMHs, with chemical doping of Sb3+shown to significantly enhance the luminescence properties, demonstrating their potential applications in solid-state lighting.

Published
2023
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65. Tunable Bright White Light Emission with Ultra‐High Color Rendering Index Induced by Trigonal Bipyramid Unit.

Author

Lin, Jiawei, Guo, Zhongnan, Liu, Kunjie, Sun, Niu, Cao, Jindong, Chen, Xin, Zhao, Jing, Liu, Quanlin, and Yuan, Wenxia

Subjects
*LIGHT emitting diodes, *METAL halides, *COLOR temperature, *MONOCHROMATIC light, *COLOR, *PHOTOLUMINESCENCE, *VISIBLE spectra
Abstract

Efficient broadband emitting organic–inorganic metal hybrids (OIMHs) have attracted great attention recently as promising single‐component white light emitters. Here a new zero‐dimensional (0D) OIMH (C13H14N)2InCl5 (C13H14N+ = N‐methyldiphenylammonium) is reported, which features unique five‐coordinated [InCl5]2− trigonal bipyramid motif. For the first time, it is demonstrated that the trigonal bipyramid units in 0D OIMH can act as luminescence centers, showing blue emission under UV light. Remarkably, incorporating Sb3+ in [InCl5]2− trigonal bipyramids induces a new dual‐band emission at 540 and 735 nm resulting from the singlet and triplet self‐trapped excitons in [SbCl5]2−, leading to complete coverage of the entire visible spectrum. The resulting emissions in (C13H14N)2InCl5:Sb3+ are tunable from cold to warm white with the correlated color temperatures changing from 5574 to 3473 K and more importantly, an ultra‐high color rendering index (CRI) up to 96 being observed, which is comparable to the highest value in hybrid metal halides. A high photoluminescence quantum yield of 46.26% is simultaneously obtained in this system. This work demonstrates that the 0D OIMH with trigonal bipyramid motif is an excellent system for realizing the single‐component white light emission with both high efficiency and ultra‐high CRI. [ABSTRACT FROM AUTHOR]

Published
2023
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66. Multiple Dirac points including potential spin-orbit Dirac points in nonsymmorphic HfGe0.92Te.

Author

Chen, Long, Zhou, Liqin, Zhou, Ying, Liu, Chen, Guo, Zhongnan, Liao, Ke, Gao, Shunye, Fan, Wenhui, Xu, Jinfeng, Guo, Yuxuan, Wang, Jia'ou, Qian, Tian, Weng, Hongming, and Wang, Gang

Abstract

The search for new materials with Dirac points has been a fascinating subject of condensed matter physics. Here we first report the growth and band structure of HfGe0.92Te single crystals featuring three different types of Dirac points. HfGe0.92Te crystallizes in a nonsymmorphic tetragonal space group P4/nmm (No. 129), having a square Ge-atom plane with vacancies of about 8%. Using angle-resolved photoemission spectroscopy (ARPES), the Dirac nodal line composed of conventional Dirac points vulnerable to spin-orbit coupling (SOC) is observed, accompanied by robust Dirac points protected by the nonsymmorphic symmetry against SOC and vacancies. In particular, spin-orbit Dirac points (SDPs) originating from the surface formed under significant SOC could exist based on ARPES and calculations. Quasi-two-dimensional (quasi-2D) characteristics are confirmed by angular-resolved magnetoresistance. HfGe0.92Te bulk crystals can be easily exfoliated to flakes with a thickness of approximately 5 nm for the quasi-2D nature. Thus, HfGe0.92Te provides a good platform to explore exotic topological phases or topological properties with three different types of Dirac points, which is a potential candidate to achieve novel 2D SDPs. [ABSTRACT FROM AUTHOR]

Published
2023
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67. (BA)10AgBi2Br19: a one-dimensional halide double perovskite with a unique Br trimer.

Author

Guo, Zhongnan, Ruan, Hang, Lin, Jiawei, Sun, Fan, Liu, Kunjie, Chen, Xin, Zhao, Jing, and Yuan, Wenxia

Subjects
*BAND gaps, *HALIDES, *PEROVSKITE, *OCTAHEDRA
Abstract

A one-dimensional (1D) halide double perovskite, (BA)10AgBi2Br19, is synthesized, which features 1D corner-sharing perovskite ribbons with a width of three octahedra. It is the first reported 1D derivative of a halide double perovskite, showing an unexpected narrow band gap (2.46 eV) due to the unique Br trimer in structure. [ABSTRACT FROM AUTHOR]

Published
2022
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75. ANi5Bi5.6+δ(A = K, Rb, and Cs): Quasi-One-Dimensional Metals Featuring [Ni5Bi5.6+δ]−Double-Walled Column with Strong Diamagnetism

Author

Zhou, Ying, Chen, Long, Wang, Yuxin, Zhu, Jinfeng, Guo, Zhongnan, Liu, Chen, Guo, Zhiying, Wang, ChinWei, Zhang, Han, Wang, Yulong, Liao, Ke, Song, Youting, Wang, Jia-ou, Chen, Dongliang, Ma, Jie, Hu, Jiangping, and Wang, Gang

Abstract

A new series of compounds, ANi5Bi5.6+δ(where A = K, Rb, and Cs) are discovered with a quasi-one-dimensional (Q1D) [Ni5Bi5.6+δ]−double-walled column and a coaxial inner one-dimensional Bi atomic chain. The columns are linked to each other by intercolumn Bi–Bi bonds and separated by an A+cation. Typical metallic behaviors with strong correlation of itinerant electrons and the Sommerfeld coefficient enhanced with the increasing cationic radius were experimentally observed and supported by first-principles calculations. Compared to AMn6Bi5(where A = K, Rb, and Cs), the enhanced intercolumn distances and the substitution of Ni for Mn give rise to strong diamagnetic susceptibilities in ANi5Bi5.6+δ. First-principles calculations reveal possible uncharged Ni atoms with even number of electrons in ANi5Bi5.6+δ, which may explain the emergence of diamagnetism. ANi5Bi5.6+δ, as Q1D diamagnetic metals with strong electron correlation, provide a unique platform to understand exotic magnetism and explore novel quantum effects.

Published
2023
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76. Cubic AgMnSbTe₃ semiconductor with a high thermoelectric performance

Author

Luo, Yubo, Xu, Tian, Ma, Zheng, Zhang, Dan, Guo, Zhongnan, Jiang, Qinghui, Yang, Junyou, Yan, Qingyu, Kanatzidis, Mercouri G., and School of Materials Science and Engineering

Subjects
Materials::Functional materials [Engineering], Semiconducting Manganese Compounds, Thermal Conductivity
Abstract

The reaction of MnTe with AgSbTe2 in an equimolar ratio (ATMS) provides a new semiconductor, AgMnSbTe3. AgMnSbTe3 crys-tallizes in an average rock-salt NaCl structure with Ag, Mn, and Sb cations statistically occupying the Na sites. AgMnSbTe3 is a p-type semiconductor with a narrow band gap of ~0.33 eV. A pair distribution function analysis indicates that local distortions are associated with the location of the Ag atoms in the lattice. Density functional theory calculations suggest a specific electronic band structure with multi-peak valence band maxima prone to energy convergence. In addition, Ag2Te nanograins precipitate at grain boundaries of AgMnSbTe3. The energy offset of the valance band edge between AgMnSbTe3 and Ag2Te is ~0.05 eV, which implies that Ag2Te precipitates exhibit a negligible effect on the hole transmission. As a result, ATMS exhibits a high power factor of ~12.2 μWcm-1K-2 at 823 K, ultralow lattice thermal conductivity of ~0.34 Wm-1K-1 (823 K), high peak ZT of ~1.46 at 823 K, and high av-erage ZT of ~0.87 in the temperature range of 400–823 K Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version This study was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under grant DESC0014520, DOE Office of Science. The User Facilities are supported by the Office of Science of the U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DEAC02-05CH11231. We acknowledge the access to facilities for high-performance computations at Northwestern University, Singapore MOE AcRF Tier 2 under Grant No. 2018-T2-1-010, Singapore A*STAR Pharos Program SERC 1527200022, Singapore A*STAR project A19D9a0096, support from FACTs of Nanyang Technological University for the sample analysis, National Natural Science Foundation of China (Grant Nos. 52002137, 51802070, 51572098, and 51632006), National Basic Research Program of China (Grant No. 2013CB632500), the Fundamental Research Funds for the Central Universities under Grant Nos. 2021XXJS008 and 2018KFYXKJC002, Natural Science Foundation of Hubei Province (Grant No. 2015CFB432), Open Fund of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology (No. 2016- KF-5), and Graduates’ Innovation Fund, Huazhong University of Science and Technology (No. 2019ygscxcy032).

Published
2021

78. Correlation of Tunable CoSi4 Tetrahedron with the Superconducting Properties of LaCoSi

Author

He, Zhengwen, primary, Song, Yuzhu, additional, Zhou, Kaiyao, additional, Guo, Shibin, additional, Wu, Junkun, additional, Yin, Congling, additional, Guo, Zhongnan, additional, He, Lunhua, additional, Huang, Qingzhen, additional, Li, Laifeng, additional, Huang, Rongjin, additional, Guo, Jiangang, additional, Xing, Xianran, additional, and Chen, Jun, additional

Published
2021
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80. Superconductivity in Co-Layered LaCoSi

Author

He, Zhengwen, primary, Huang, Rongjin, additional, Zhou, Kaiyao, additional, Liu, Ye, additional, Guo, Shibin, additional, Song, Yuzhu, additional, Guo, Zhongnan, additional, Hu, Shuxian, additional, He, Lunhua, additional, Huang, Qingzhen, additional, Li, Laifeng, additional, Zhang, Jingyan, additional, Wang, Shouguo, additional, Guo, Jiangang, additional, Xing, Xianran, additional, and Chen, Jun, additional

Published
2021
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81. Local Distortions and Metal–Semiconductor–Metal Transition in Quasi-One-Dimensional Nanowire Compounds AV3Q3Oδ (A = K, Rb, Cs and Q = Se, Te)

Author

Guo, Zhongnan, primary, Sun, Fan, additional, Puggioni, Danilo, additional, Luo, Yubo, additional, Li, Xiaotong, additional, Zhou, Xiuquan, additional, Chung, Duck Young, additional, Cheng, Erjian, additional, Li, Shiyan, additional, Rondinelli, James M., additional, Yuan, Wenxia, additional, and Kanatzidis, Mercouri G., additional

Published
2021
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85. High-efficiency red photoluminescence achieved by antimony doping in organic–inorganic halide (C11H24N2)2[InBr6][InBr4].

Author

Lin, Jiawei, Guo, Zhongnan, Sun, Niu, Liu, Kunjie, Chen, Xin, Zhao, Jing, Liu, Quanlin, and Yuan, Wenxia

Abstract

Organic–inorganic metal halides (OIMHs) exhibit various crystal structures and strong broadband emission, showing enormous potential for solid-state lighting and displays. In this work, we report a new lead-free OIMH (C11H24N2)2[InBr6][InBr4], which adopts a typical zero dimensional (0D) structure with the inorganic polyhedra separated by the large organic cations. Different from the general 0D In-based OIMHs with single octahedral [InBr6]3− units, (C11H24N2)2[InBr6][InBr4] contains both [InBr6]3− octahedra and [InBr4]− tetrahedra. It shows a large optical bandgap of 3.95 eV and excellent ambient stability. In addition, Sb dopants can be included in the structure, and an obvious preference for substituting the In atoms in the [InBr6]3− octahedra has been determined by analyzing the related bond lengths and polyhedral distortion. (C11H24N2)2[InBr6][InBr4] exhibits a broadband red emission (660 nm) that is ascribed to self-trapped excitons (STEs) in octahedral [InBr6]3−, and the photoluminescence quantum yield (PLQY) can be significantly enhanced from 8% to 61% upon Sb doping, mainly as a result of the extra photo-induced excitons from [SbBr6]3−. Density functional calculations reveal the direct bandgap nature of (C11H24N2)2[InBr6][InBr4], which is transferred to an indirect band gap after Sb doping due to the formation of the intra-gap band. A white light-emitting diode (WLED) was fabricated by combining the red emissive (C11H24N2)2[InBr6][InBr4]:Sb3+ and commercial green and blue phosphors, exhibiting a high color-rendering index of 88.7. Our work reports high-efficiency red photoluminescence (PL) in this special 0D double-inorganic-unit system, and demonstrates its potential applications for solid-state lighting. [ABSTRACT FROM AUTHOR]

Published
2022
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91. Structure and Optical Properties of Hybrid-Layered-Double Perovskites (C8H20N2)2AgMBr8(M = In, Sb, and Bi)

Author

Ruan, Hang, Guo, Zhongnan, Lin, Jiawei, Liu, Kunjie, Guo, Lingling, Chen, Xin, Zhao, Jing, Liu, Quanlin, and Yuan, Wenxia

Abstract

The Pb-free hybrid-layered-double perovskites (HLDPs) have been proposed as green and stable semiconducting materials for optoelectronic devices, but the synthesized members are still limited. Here, we report the synthesis of three new HLDPs, (C8H20N2)2AgMBr8(M = In, Sb, and Bi), by a solution method using 1,4-bis(ammoniomethyl)cyclohexane (C8H20N22+) as the organic spacing cation. All three of these HLDPs show ⟨100⟩-oriented layered structures with Ag and In/Sb/Bi order arranged in corner-sharing octahedral layers. The first-principle calculations indicate the indirect-gap nature of (C8H20N2)2AgInBr8and (C8H20N2)2AgSbBr8, while their Bi counterpart shows a direct band gap after considering spin–orbit coupling. The band gaps obtained by diffuse-reflectance spectroscopy are 3.11, 2.60, and 2.70 eV for M = In, Sb, and Bi, respectively. (C8H20N2)2AgInBr8shows a broadband red emission centered at 690 nm, and it is mainly attributed to the self-trapped-excitons mechanism. Our results not only provide a series of new “Pb-free” HLDPs with chemical diversity but also help us to further understand the structure–property relationships of HLDP materials.

Published
2021
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96. Correlation of Tunable CoSi4Tetrahedron with the Superconducting Properties of LaCoSi

Author

He, Zhengwen, Song, Yuzhu, Zhou, Kaiyao, Guo, Shibin, Wu, Junkun, Yin, Congling, Guo, Zhongnan, He, Lunhua, Huang, Qingzhen, Li, Laifeng, Huang, Rongjin, Guo, Jiangang, Xing, Xianran, and Chen, Jun

Abstract

It is known that as the FeAs4tetrahedron in the Fe-based superconductor is close to the regular tetrahedron, critical temperature (Tc) can be greatly increased. Recently, a Co-based superconductor of LaCoSi (4 K) with “111” structure was found. In this work, we improve the Tcof LaCoSi through structural regulation. Tccan be increased by the chemical substitution of Co by Fe, while the superconductivity is suppressed by the Ni substitution. The combined analysis of neutron and synchrotron X-ray powder diffractions reveals that the change of the Si–Co–Si bond angles of the CoSi4tetrahedron is possibly responsible for the determination of superconducting properties. The Fe chemical substitution is favorable for the formation of the regular tetrahedron of CoSi4. The present new Co-based superconductor of LaCoSi provides a possible method to enhance the superconductivity performance of the Co-based superconductors via controlling Co-based tetrahedra similar to those well established in the Fe-based superconductors.

Published
2021
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97. Light-Emitting 0D Hybrid Metal Halide (C3H12N2)2Sb2Cl10with Antimony Dimers

Author

Li, Mingyang, Lin, Jiawei, Liu, Kunjie, Fan, Liubing, Wang, Na, Guo, Zhongnan, Yuan, Wenxia, Zhao, Jing, and Liu, Quanlin

Abstract

Low-dimensional organic–inorganic metal halides (OIMHs), as emerging light-emitting materials, have aroused widespread attention owing to their unique structural tunability and photoelectric characteristics. OIMHs are also promising materials for optoelectronic equipment, light-emitting diodes, and photodetectors. In this study, (C3H12N2)2Sb2Cl10(C3H12N22+is an N-methylethylenediamine cation), a new zero-dimensional OIMH, has been reported, and (C3H12N2)2Sb2Cl10possesses a P21/nspace group. The (C3H12N2)2Sb2Cl10structure contains [Sb2Cl10]4–dimers (composed of two edge-sharing [SbCl6]3–octahedra) that are surrounded by C3H12N22+cations. The experimental band gap of (C3H12N2)2Sb2Cl10is 3.80 eV, and density functional theory calculation demonstrates that (C3H12N2)2Sb2Cl10possesses a direct band gap, with the edge of the band gap mainly contributed from the inorganic units. (C3H12N2)2Sb2Cl10exhibits good ambient and thermal stability. Under 395 nm excitation at room temperature, (C3H12N2)2Sb2Cl10exhibits a broad emission with a full width at half-maximum of ∼114 nm, peaking at 480 nm, and the broad emission was ascribed to self-trapped exciton emission.

Published
2021
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98. Three phase three level inverter digital control based on over sample and multi-time calculation

Author

Ben Bing, Zhao Xiaojun, Guo Zhongnan, and Zhang Chunjiang

Subjects
Engineering, Total harmonic distortion, business.industry, 020208 electrical & electronic engineering, 02 engineering and technology, Three-phase, Control theory, Hardware_INTEGRATEDCIRCUITS, 0202 electrical engineering, electronic engineering, information engineering, Electronic engineering, Inverter, Waveform, Digital control, Grid-tie inverter, business, Digital signal processing, Voltage
Abstract

The principle of a diode neutral point clamped three-phase three-level inverter with neutral line was analyzed, and the mathematical model of the main circuit is established on the basis of the operation principle. The oversample and multi-time calculation control strategy was proposed to reduce the typical delay in digital control and improve the system calculation accuracy, lower the inverter output voltage THD. In order to further improve the inverter output voltage waveform, the logic external execution was also proposed. The proposed control method was verified on a 20kVA inverter controlled by microchip processor IC30F5015 DSP. The experiment results indicated that the THD of the inverter output voltage is decreased considerably.

Published
2016
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99. A new balance control method of three-level converter NPP

Author

Li Pengcheng, Chai Xiuhui, Guo Zhongnan, and Zhang Chunjiang

Subjects
Engineering, Correctness, business.industry, 020209 energy, 020208 electrical & electronic engineering, Control engineering, 02 engineering and technology, Three level, DC-BUS, Dc voltage, Control theory, Distributed generation, Frequency characteristic, 0202 electrical engineering, electronic engineering, information engineering, business, Control methods
Abstract

With the NPC converter widely applied to distributed generation system, the ability to ensure the DC bus neutral-point potential (NPP) balance has a crucial impact on the system. Research on grid-connected NPC three-level converter, in this paper, mathematical model of NPP fluctuation is established firstly, the mechanism of NPP ac-dc fluctuations is analyzed, the relationship between NPP error calculation and system operation mode (rectifier-mode or inverter-mode) is deduced, NPP control model based on equalizing loop is established. Secondly, the inherent relationship for NPP balancing control and controller parameter tuning method are given by theoretical analysis. In order to maximize suppress NPP AC fluctuations, the paper proposes a method that controller parameters is designed according to the largest open-loop shear frequency by system frequency characteristic analysis. The NPP Control method has the following advantages: effectively suppressing of NPP ac/dc fluctuations at the same time, positive and negative DC bus voltage fast dynamic response, high utilization rate of dc voltage. Finally, the correctness of the theoretical analysis is verified by MATLAB simulation.

Published
2016
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