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Fine-Tuning Crystal Structures of Lead Bromide Perovskite nanocrystals through Trace Cadmium(II) Doping for Efficient Color-Saturated Green LEDs

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Angewandte Chemie 2024年第26期136卷

作者： Dr. Jianfeng Zhang Dr. Junhui Wang Dr. Lei Cai Dr. Sheng Wang Prof. Kaifeng Wu Prof. Baoquan Sun Prof. Weitao Zheng Dr. Stephen V. Kershaw Prof. Guohua Jia Prof. Xiaoyu Zhang Prof. Andrey L. Rogach Prof. Xuyong Yang Key Laboratory of Advanced Display and System Applications of Ministry of Education Shanghai University Shanghai 200072 P. R. China Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu 611731 P. R. China State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 Liaoning P. R. China University of Chinese Academy of Sciences Beijing 100049 P. R. China Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices Institute of Functional Nano & Soft Materials (FUNSOM) Soochow University Suzhou 215123 P. R. China Key Laboratory of Automobile Materials Ministry of Education College of Materials Science and Engineering Jilin University Changchun 130012 P. R. China Department of Materials Science and Engineering Centre for Functional Photonics (CFP) City University of Hong Kong Hong Kong SAR 999077 P. R. China School of Molecular and Life Science Curtin University Bentley WA 6102 Australia

Decreasing perovskite nanocrystal size increases radiative recombination due to the quantum confinement effect, but also increases the Auger recombination rate which leads to carrier imbalance in the emitting layers of electroluminescent devices. Here, we overcome this trade-off by increasing the exciton effective mass without affecting the size, which is realized through the trace Cd 2+ doping of formamidinium lead bromide perovskite nanocrystals. We observe an ~2.7 times increase in the exciton binding energy benefiting from a slight distortion of the [BX 6 ] 4− octahedra caused by doping in the case of that the Auger recombination rate is almost unchanged. As a result, bright color-saturated green emitting perovskite nanocrystals with a photoluminescence quantum yield of 96 % are obtained. Cd 2+ doping also shifts up the energy levels of the nanocrystals, relative to the Fermi level so that heavily n -doped emitters convert into only slightly n -doped ones; this boosts the charge injection efficiency of the corresponding light-emitting diodes. The light-emitting devices based on those nanocrystals reached a high external quantum efficiency of 29.4 % corresponding to a current efficiency of 123 cd A −1 , and showed dramatically improved device lifetime, with a narrow bandwidth of 22 nm and Commission Internationale de I'Eclairage coordinates of (0.20, 0.76) for color-saturated green emission for the electroluminescence peak centered at 534 nm, thus being fully compliant with the latest standard for wide color gamut displays.

关键词： perovskite nanocrystals light-emitting diode exciton binding energy auger recombination cadmium (II) doping

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Mass-manufactural Lanthanide-based Ultraviolet C microlasers

Mass-manufactural Lanthanide-based Ultraviolet C Microlasers

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第九届国际稀土开发与应用研讨会暨2019中国稀土学会学术年会

作者： Limin Jin Yunkai Wu Yujie Wang Yuqi Zhang Zhiying Li Xian Chen Wenfei Zhang Shumin Xiao Qinghai Song State Key Laboratory on Tunable Laser Technology Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information SystemShenzhen Graduate SchoolHarbin Institute of Technology College of Materials Science of Engineering Shenzhen University Shenzhen Key Laboratory of Laser Engineering College of Optoelectronic EngineeringShenzhen University Collaborative Innovation Center of Extreme Optics Shanxi University

Lanthanide(Ln)-based ultraviolet C（UVC） microlasers are highly desirable for diagnostics and phototherapy. Despite of their progresses, the potential applications of UVC microlasers are strongly hindered by their low optical gain, weak light confinements, and poor device repeatability. Herein, we report a novel approach to all-in-one solve the above limitations and realize mass-manufactural UVC microlasers. The gain coefficient at 289 nm has been improved from two aspects, i.e. the enhanced absorption via LiYbF:Tm（lmoI%）@LiYbF@LiLuF core-shell-shell nanocrystals and the suppression of competitive ultraviolet ***, by spin-coating the solution onto patterned SiO substrate, high-quality Ln-based microdisks are self-assembly formed on each SiO pillar and UVC whispering-gallery-mode lasers have been realized. The resulted lasing threshold is an order of magnitude smaller than the shortest deep-ultraviolet emission at 310 nm. Importantly,the lasing wavelengths and mode numbers of UVC lasers are highly controllable and repeatable, making them suitable for mass-production for the first time.

关键词： lanthanide-doped upconversion nanocrystals on-chip microlaser array ultraviolet C lasing emission high controllability whispering gallery modes

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Gain-Assisted Plasmon Resonance Narrowing and Its Application in Sensing

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Physical Review Applied 2019年第4期11卷 044030-044030页

作者： Lijun Meng Ding Zhao Yuanqing Yang F. Javier García de Abajo Qiang Li Zhichao Ruan Min Qiu Zhejiang Province Key Laboratory of Quantum Technology and Device Department of Physics and State Key Laboratory of Modern Optical Instrumentation Zhejiang University Hangzhou Zhejiang China ICFO-Institut de Ciencies Fotoniques The Barcelona Institute of Science and Technology 08860 Castelldefels (Barcelona) Spain State Key Laboratory of Modern Optical Instrumentation Zhejiang University Hangzhou 310027 China DTU Nanolab Technical University of Denmark 2800 Kongens Lyngby Denmark SDU Nano Optics University of Southern Denmark Campusvej 55 DK-5230 Odense Denmark ICREA-Institució Catalana de Recerca i Estudis Avançats Passeig Lluís Companys 23 08010 Barcelona Spain Institute of Advanced Technology Westlake Institute for Advanced Study 18 Shilongshan Road Hangzhou 310024 Zhejiang Province China Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province School of Engineering Westlake University 18 Shilongshan Road Hangzhou 310024 Zhejiang Province China

We demonstrate the viability of using high-order modes in localized optical resonances combined with gain media to dramatically reduce the linewidths of absorption spectra. Our theoretical study provides a rational design route for small-footprint absorption with a high quality factor, which is typically a trade-off for plasmonic light absorbers. Specifically, we design and numerically investigate a metal-insulator-metal absorber and a graphene Salisbury screen. Additionally, we study the potential application of these structures in sensing in order to achieve higher performance compared with conventional sensors based on the fundamental mode. Our approach, which can readily operate in a multiplexed fashion, has the potential for sensing minute amounts of analytes with a high figure of merit.

关键词： Analytical chemistry Integrated optics Light propagation, transmission & absorption Metamaterials nanoantennas Plasmonics Solid-state detectors Resonance techniques

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Valley filtering effect of phonons in graphene with a grain boundary

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Physical Review B 2019年第6期99卷 064302-064302页

作者： Xiaobin Chen Yong Xu Jian Wang Hong Guo State Key Laboratory on Tunable laser Technology and Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System School of Science Harbin Institute of Technology Shenzhen 518055 China Department of Physics and the Center of Theoretical and Computational Physics The University of Hong Kong Hong Kong China Collaborative Innovation Center of Quantum Matter and State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 People's Republic of China The University of Hong Kong Shenzhen Institute of Research and Innovation Shenzhen 518053 China College of Physics and Energy Shenzhen University Shenzhen 518060 China Department of Physics 3600 University McGill University Montreal Quebec H3A 2T8 Canada

Due to their possibility to encode information and realize low-energy-consumption quantum devices, control and manipulation of the valley degree of freedom have been widely studied in electronic systems. In contrast, the phononic counterpart—valley phononics—has been largely unexplored, despite the importance in both fundamental science and practical applications. In this work, we demonstrate that the control of “valleys” is also applicable for phonons in graphene by using a grain boundary. In particular, perfect valley filtering effect is observed at certain energy windows for flexural modes and found to be closely related to the anisotropy of phonon valley pockets. Moreover, valley filtering may be further improved using Fano-like resonance. Our findings reveal the possibility of valley phononics, paving the road towards purposeful phonon engineering and future valley phononics.

关键词： Ballistic transport Grain boundaries Phonons Valleytronics Graphene First-principles calculations Nonequilibrium Green's function

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Simulation and structure optimization of triboelectric nanogenerators considering the effects of parasitic capacitance

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nano Research 2017年第1期10卷 157-171页

作者： Keren Dai Xiaofeng Wang Simiao Niu Fang Yi Yajiang Yin Long Chen Yue Zhang Zheng You Collaborative Innovation Center for Micro/Nano Fabrication Device and System State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision Instrument Tsinghua University Beijing 100084 China School of Materials Science and Engineering Georgia Institute of Technology Atlanta GA30332-0245 USA State Key Laboratory for Advanced Metals and Materials School of Materials Science and Engineering Bei)ing Municipal Key Laboratory of New Energy Materials and Technologies University of Science and Technology Beijing Beijing 100083 China Broadcom Ltd. 2901 Via Fortuna #400 Austin TX 78746 USA

Parasitic capacitance is an unavoidable and usually unwanted capacitance that exists in electric circuits, and it is the most important second-order non-ideal effect that must be considered while designing a triboelectric nanogenerator （TENG） because its magnitude is comparable to the magnitude of the TENG capacitance. This paper investigates the structure and performance optimization of TENGs through modeling and simulation, taking the parasitic capacitance into account. Parasitic capacitance is generally found to cause severe performance degradation in TENGs, and its effects on the optimum matching resistance, maximum output power, and structural figures-of-merit （FOMs） of TENGs are thoroughly investigated and discussed. Optimum values of important structural parameters such as the gap and electrode length are determined for the different working modes of TENGs, systematically demonstrating how these optimum structural parameters change as functions of the parasitic capacitance. Additionally, it is demonstrated that the parasitic capacitance can improve the height tolerance of the metal freestanding-mode TENGs. This work provides a theoretical foundation for the structure and performance optimization of TENGs for practical applications and promotes the development of mechanical energy-harvesting techniques.

关键词： triboelectric nanogenerator parasitic capacitance figure of merit structure optimization performance optimization

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Thick SU8 microstructures prepared by broadband UV lithography and the applications in MEMS devices

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Optoelectronics Letters 2016年第3期12卷 182-187页

作者：李东玲温志渝尚正国佘引 National Key Laboratory of Fundamental Science of Novel Micro/Nano Device and System Technology Key Laboratory of Optoelectronic Technology and System of the Education Ministry of China Micro System Reaserch CenterChongqing University

Thick SU8 microstructures with high aspect ratio and good side wall quality were fabricated by ultraviolet （UV） lithography, and the processing parameters were comprehensively studied. It proves that the adhesion of SU8 on silicon （Si） substrates is influenced by Si-OH on the surface, and can be improved by the HF treatment. Cracks and de- lamination are caused by large internal stress during fabrication process, and are significantly influenced by soft bake and post-exposure bake processes. The internal stress is reduced by a low post-exposure bake exposure tem- perature of 85 ℃ for 40 rain. A three-step soft bake enhances the reflowing ofSU8 photoresist, and results in uni- form surface and less air bubbles. The vertical side wall is obtained with the optimized exposure dose of 800 mJ/cm2 for the thickness of 160 μm. Using the optimized fabrication process combined with a proper structure design, dense SU8 micro pillars are achieved with the aspect ratio of 10 and the taper angle of 89.86°. Finally, some possible ap- plications of SU8 in micro-electromechanical system （MEMS） device are developed and demonstrated.

关键词： MEMS器件紫外光刻微结构应用微机电系统烘烤过程编写宽带

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Valley filtering effect of phonons in graphene with a grain boundary

arXiv

引用

arXiv 2019年

作者： Chen, Xiaobin Xu, Yong Wang, Jian Guo, Hong State Key Laboratory on Tunable laser Technology Ministry of Industry Information Technology Key Lab of Micro-Nano Optoelectronic Information System School of Science Harbin Institute of Technology Shenzhen518055 China Department of Physics Center of Theoretical and Computational Physics University of Hong Kong Hong Kong Hong Kong Collaborative Innovation Center of Quantum Matter State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing100084 China University of Hong Kong Shenzhen Institute of Research and Innovation Shenzhen518053 China College of Physics and Energy Shenzhen University Shenzhen518060 China Department of Physics 3600 University McGill University MontrealQCH3A 2T8 Canada

Due to their possibility to encode information and realize low-energy-consumption quantum devices, control and manipulation of the valley degree of freedom have been widely studied in electronic systems. In contrast, the phononic counterpart–valley phononics–has been largely unexplored, despite the importance in both fundamental science and practical applications. In this work, we demonstrate that the control of "valleys" is also applicable for phonons in graphene by using a grain boundary. In particular, perfect valley filtering effect is observed at certain energy windows for flexural modes and found to be closely related to the anisotropy of phonon valley pockets. Moreover, valley filtering may be further improved using Fano-like resonance. Our findings reveal the possibility of valley phononics, paving the road towards purposeful phonon engineering and future valley phononics. Copyright © 2019, The Authors. All rights reserved.

关键词： Landforms

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Design and fabrication of an surface acoustic wave resonator based on AlN/4H-SiC material for harsh environments

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Journal of Zhejiang University-science A(Applied Physics & Engineering) 2017年第1期18卷 67-74页

作者： Wei-zhong WANG Ji LIANG Yong RUAN Wei PANG Zheng YOU Collaborative Innovation Center for Micro/Nano Fabrication Device and System State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision Instrument Tsinghua University Beijing 100084 China State Key Laboratory of Precision Measurement Technology and lnstruments Tianjin University Tianjin 300072 China

Surface acoustic wave （SAW） sensors and micro-electromechanical system （MEMS） technology provide a promising solution for measurement in harsh environments such as gas turbines. In this paper, a SAW resonator （size： 1107μm× 721 μm） based on the AlN/4H-SiC multilayer structure is designed and simulated. A MEMS-compatible fabrication process is employed to fabricate the resonator. The results show that highly c-axis-oriented AlN thin films deposited on the 4H-SiC substrate are obtained, with that the diffraction peak of AlN is 36.10° and the lowest full width at half maximum （FWHM） value is only 1.19°. The test results of the network analyzer are consistent with the simulation curve, which is very encouraging and indicates that our work is a significant attempt to solve the measurement problems mainly including high temperature stability of sensitive structures and the heat transmission of leads in harsh environments. It is essential to get the best performance of SAW resonator, optimize and characterize the behaviors in high temperatures in future research.

关键词： Surface acoustic wave （SAW） resonator AlN/4H-SiC Harsh environment micro-electromechanical system（MEMS） technology Gas turbine

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Phase-encoded RF signal generation based on an integrated 49GHz micro-comb optical source

arXiv

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arXiv 2019年

作者： Xu, Xingyuan Tan, Mengxi Wu, Jiayang Boes, Andreas Corcoran, Bill Nguyen, Thach G. Chu, Sai T. Little, Brent E. Morandotti, Roberto Mitchell, Arnan Moss, David J. Centre for Micro-Photonics Swinburne University of Technology HawthornVIC3122 Australia School of Engineering RMIT University MelbourneVIC3001 Australia Department of Electrical and Computer System Engineering Monash University ClaytonVIC3168 Australia Department of Physics City University of Hong Kong Tat Chee Avenue Hong Kong State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Science Xi'An China INSR-Énergie Matériaux et Télécommunications 1650 Boulevard Lionel-Boulet VarennesQCJ3X 1S2 Canada Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu610054 China

We demonstrate photonic RF phase encoding based on an integrated micro-comb source. By assembling single-cycle Gaussian pulse replicas using a transversal filtering structure, phase encoded waveforms can be generated by programming the weights of the wavelength channels. This approach eliminates the need for RF signal generators for RF carrier generation or arbitrary waveform generators for phase encoded signal generation. A large number of wavelengths—up to 60—were provided by the microcomb source, yielding a high pulse compression ratio of 30. Reconfigurable phase encoding rates ranging from 2 to 6 Gb/s were achieved by adjusting the length of each phase code. This work demonstrates the significant potentials of this microcomb-based approach to achieve high-speed RF photonic phase encoding with low cost and footprint. Copyright © 2019, The Authors. All rights reserved.

关键词： Signal encoding

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Photonic based phase-encoded RF signal generation for advanced radar systems with a 49GHz soliton crystal micro-comb optical source

TechRxiv

引用

TechRxiv 2019年

作者： Xu, Xingyuan Tan, Mengxi Wu, Jiayang Boes, Andreas Corcoran, Bill Nguyen, Thach G. Chu, Sai T. Little, Brent E. Morandotti, Roberto Mitchell, Arnan Moss, David J. The Centre for Micro-Photonics Swinburne University of Technology HawthornVIC3122 Australia The School of Engineering RMIT University MelbourneVIC3001 Australia The Department of Electrical and Computer System Engineering Monash University ClaytonVIC3168 Australia The Department of Physics City University of Hong Kong Tat Chee Avenue Hong Kong State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Science Xi'An China INSR-Énergie Matériaux et Télécommunications 1650 Boulevard Lionel-Boulet VarennesQCJ3X 1S2 Canada The Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu610054 China

关键词： Signal encoding

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