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Chemical vapor deposition growth of single-crystalline cesium lead halide microplatelets and heterostructures for optoelectronic applications

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Nano Research 2017年第4期10卷 1223-1233页

作者： Yiliu Wang Xun Guan dehui li Hung-Chieh Cheng Xidong Duan Zhaoyang lin Xiangfeng Duan Department of Chemistry and Biochemistry University of California Los Angeles Los Angeles CA 90095 USA State Key Laboratory for Chemo/Biosensing and Chemometrics College of Chemistry and Chemical Engineering Hunan University Changsha 410082 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Department of Materials Science and Engineering University of California Los Angeles Los Angeles CA 90095 USA California NanoSystems Institute University of California Los Angeles Los Angeles CA 90095 USA

Organic-inorganic hybrid halide perovskites, such as CH3NHgPbI3, have emerged as an exciting class of materials for solar photovoltaic applications; however, they are currently plagued by insufficient environmental stability. To solve this issue, all-inorganic halide perovskites have been developed and shown to exhibit significantly improved stability. Here, we report a single-step chemical vapor deposition growth of cesium lead halide （CsPbX3） microcrystals. Optical microscopy studies show that the resulting perovskite crystals predominantly adopt a square-platelet morphology. Powder X-ray diffraction （PXRD） studies of the resulting crystals demonstrate a highly crystalline nature, with CsPbC13, CsPbBr3, and CsPbI3 showing tetragonal, monoclinic, and orthorhombic phases, respectively. Scanning electron microscopy （SEM） and atomic force microscopy （AFM） studies show that the resulting platelets exhibit well-faceted structures with lateral dimensions of the order of 10-50 μm, thickness around 1 μm, and ultra-smooth surface, suggesting the absence of obvious grain boundaries and the single-crystalline nature of the individual microplatelets. Photoluminescence （PL） images and spectroscopic studies show a uniform and intense emission consistent with the expected band edge transition. Additionally, PL images show brighter emission around the edge of the platelets, demonstrating a wave-guiding effect in high-quality crystals. With a well-defined geometry and ultra-smooth surface, the square platelet structure can function as a whispering gallery mode cavity with a quality factor up to 2,863 to support laser emission at room temperature. Finally, we demonstrate that such microplatelets can be readily grown on a variety of substrates, including silicon, graphene, and other two-dimensional materials such as molybdenum disulfide, which can readily allow the construction of heterostructure optoelectronic devices, including a graphene/perovskite/ graphene vertically-stacked pho

关键词： chemical vapor deposition inorganic perovskite microplatelets photoluminescence optical cavity photodetection

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Climate and fire drivers of forest composition and openness in the Changbai Mountains since the Late Glacial

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Forest Ecosystems 2023年第4期10卷 448-458页

作者： Meng Meng Sandy P.Harrison Dongmei Jie Nannan li Baojian liu dehui li Guizai Gao Honghao Niu School of Geographical Sciences Northeast Normal UniversityChangchun130024China Geography&Environmental Science University of ReadingWhiteknightsReadingRG66AHUK Leverhulme Centre for Wildfires Environment and SocietyImperial College LondonSouth KensingtonLondonSW72BWUK Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains Ministry of EducationChangchun130024China Institute for Peat and Mire Research State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation RestorationNortheast Normal UniversityChangchun130024China Key Laboratory for Vegetation Ecology Ministry of EducationChangchun130024China HaiZhou Senior High School Lianyungang222023China College of Resources and Environment Hebei Normal UniversityShijiazhuang050010China School of Archaeology Jilin UniversityChangchun130015China

Ongoing climate changes have a direct impact on forest growth;they also affect natural fire regimes,with further implications for forest *** of how these will affect forests on decadal-to-centennial timescales is *** we use reconstructions of past vegetation,fire regimes and climate during the Holocene to examine the relative importance of changes in climate and fire regimes for the abundance of key tree species in northeastern *** reconstructed vegetation changes and fire regimes based on pollen and charcoal records from Gushantun *** then used generalized linear modelling to investigate the impact of reconstructed changes in summer temperature,annual precipitation,background levels of fire,fire frequency and fire magnitude to identify the drivers of decadal-to-centennial changes in forest openness and *** in climate and fire regimes have independent impacts on the abundance of the key tree *** variables are generally more important than fire variables in determining the abundance of individual *** is the only determinant of forest openness,but summer temperature is more important than precipitation for individual tree taxa with warmer summers causing a decrease in cold-tolerant conifers and an increase in warmth-demanding broadleaved *** background level and fire frequency have negative relationships with the abundance of most tree taxa;only Pinus increases as fire frequency *** magnitude of individual fires does not have a significant impact on species abundance on this *** climate and fire regime characteristics must be considered to understand changes in forest composition on the decadal-to-centennial *** are differences,both in sign and magnitude,in the response of individual tree species to individual drivers.

关键词： Forest composition Climate change Fire regime Fire frequency Changbai Mountains Holocene Generalized linear model

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Two/Quasi-two-dimensional perovskite-based heterostructures:construction,properties and applications

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International Journal of Extreme Manufacturing 2023年第1期5卷 100-123页

作者： Haizhen Wang Yingying Chen dehui li School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074People’s Republic of China Wuhan National Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430074People’s Republic of China

Two-dimensional(2D)/quasi-2D organic-inorganic halide perovskites are regarded as naturally formed multiple quantum wells with inorganic layers isolated by long organic chains,which exhibit layered structure,large exciton binding energy,strong nonlinear optical effect,tunable bandgap via changing the layer number or chemical composition,improved environmental stability,and excellent optoelectronic *** extensive choice of long organic chains endows 2D/quasi-2D perovskites with tunable electron-phonon coupling strength,chirality,or ferroelectricity *** particular,the layered nature of 2D/quasi-2D perovskites allows us to exfoliate them to thin plates to integrate with other materials to form heterostructures,the fundamental structural units for optoelectronic devices,which would greatly extend the functionalities in view of the diversity of 2D/quasi-2D *** this paper,the recent achievements of 2D/quasi-2D perovskite-based heterostructures are ***,the structure and physical properties of 2D/quasi-2D perovskites are *** then discuss the construction and characterizations of 2D/quasi-2D perovskite-based heterostructures and highlight the prominent optical properties of the constructed ***,the potential applications of 2D/quasi-2D perovskite-based heterostructures in photovoltaic devices,light emitting devices,photodetectors/phototransistors,and valleytronic devices are ***,we summarize the current challenges and propose further research directions in the field of 2D/quasi-2D perovskite-based heterostructures.

关键词： 2D perovskites heterostructures characterization optical properties applications

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Self-trapped excitons in two-dimensional perovskites

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Frontiers of Optoelectronics 2020年第3期13卷 225-234页

作者： Junze li Haizhen WANG dehui li School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China Wuhan National Laboratory for Optoclectronics Huazhong University of Science and TcchnologyWuhan 430074China

With strong electron-phonon coupling,the self-trapped excitons are usually formed in materials,which leads to the local lattice distortion and localized *** self-trapping strongly depends on the dimensionality of the *** the three dimensional case,there is a potential barrier for self-trapping,whereas no such barrier is present for quasi-one-dimensional ***-dimensional(2D)systems are marginal cases with a much lower potential barrier or nonex istent potential barrier for the self-trapping,leading to the easier formation of self-trapped ***-trapped excitons emission exhibits a broadband emission with a large Stokes shift below the bandgap.2D perovskites are a class of layered structure material with unique optical properties and would find potential promising *** particular,self-trapped excitons are present in 2D per-ovskites and can significantly influence the optical and electrical properties of 2D perovskites due to the soft characteristic and strong electron-phonon ***,we summarized the luminescence characteristics,origins,and characterizations of self-trapped excitons in 2D perovskites and finally gave an introduction to their applications in optoelectronics.

关键词： self-trapped exciton(STE) two-dimensional(2D)perovskites broadband emission electron-phonon coupling optoelectronic applications

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Strain-induced spatially indirect exciton recombination in zinc-blende/wurtzite CdS heterostructures

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Nano Research 2015年第9期8卷 3035-3044页

作者： dehui li Yang liu Maria de la Mata Cesar Magen Jordi Arbiol Yuanping Feng Qihua Xiong Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Institut de Ciencia de Materials de Barcelona ICMAB-CSIC Campus de la UAB 08193 Bellaterra Catalonia Spain Laboratofio de Microscopias Avanzadas (LMA) Instituto de Nanociencia de Aragon (INA) ARAID and Departamento de Fisica de la Materia Condensada Universidad de Zaragoza 50018 Zaragoza Spain Institucio Catalana de Recerca i Estudis Avancats (ICREA) 08010 Barcelona Catalonia Spain Institut Catala de Nanociencia i Nanotecnologia (ICN2) Campus UAB 08193 Bellaterra Catalonia Spain Department of Physics National University of Singapore 2 Science Drive 3 Singapore 117542 Singapore Division of Microelectronics School of Electrical and Electronic Engineering Nanyang Technological University Singapore 639798Singapore

Strain engineering provides an effective mean of tuning the fundamental properties of semiconductors for electric and optoelectronic applications. Here we report on how the applied strain changes the emission properties of hetero- structures consisting of different crystalline phases in the same CdS nanobelts. The strained portion was found to produce an additional emission peak on the low-energy side that was blueshifted with increasing strain. Furthermore, the additional emission peak obeyed the Varshni equation with temperature and exhibited the band-filling effect at high excitation power. This new emission peak may be attributed to spatially indirect exciton recombination between different crystalline phases of CdS. First-principles calculations were performed based on the spatially indirect exciton recombination, and the calculated and experimental results agreed with one another. Strain proved to be capable of enhancing the anti-Stokes emission, suggesting that the efficiency of laser cooling may be improved by strain engineering.

关键词： strain,CdS nanobelts,photoluminescence,spatially indirect excitonrecombination,inter-crystalline phasetransition

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Halide perovskites: from materials to optoelectronic devices

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Frontiers of Optoelectronics 2020年第3期13卷 191-192页

作者： Jiang TANG dehui li School of Optical and Electronic Information Wuhan National Laboratory for OptoelectronicsHuazhong University of Science and TechnologyWuhan 430074China

Halide perovskites have been extensively studied in last decade partially due to the unprecedentedly rapid increase of power conversion efficiency of perovskite based solar *** addition to the solar cells,perovskite based optoelectronic devices such as photodetectors and light emitting devices have also been demonstrated with impressive performance,benefited from the large absorption coefficient,tunable band gap,defect tolerance and long carrier diffusion *** significant progress has been made in these fields,a few challenges including Iong-term stability and toxicity of lead greatly limit their *** effort has been put into those fields to address the long-last issues from aspects of fundamental understanding of their photophysics,material engineering and performance *** special issue on“Halide perovskites:from materials to optoelectronic devices”including one comment,four reviews,and five original research articles covers all topics mentioned.

关键词： optimization. perovskite mentioned

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Reduced graphene oxide/silicon nanowire hetero- structures with enhanced photoactivity and superior photoelectrochemical stability

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Nano Research 2015年第9期8卷 2850-2858页

作者： Xing Zhong Gongming wang Benjamin Papandrea Mufan li Yuxi Xu Yu Chen Chih-Yen Chen Hailong Zhou Teng Xue Yongjia li dehui li Yu Huang Xiangfeng Duan Department of Chemistry and Biochemistry University of California Los Angeles Los Angeles California 90095 USA Department of Materials Science and Engineering University of California Los Angeles California 90095 USA California Nanosystems Institute University of California Los Angeles California 90095 USA

Silicon nanowires （SiNWs） have been widely studied as light harvesting antennas in photocatalysts due to their ability to absorb broad-spectrum solar radiation, but they are typically limited by poor photoelectrochemical stability. Here, we report the synthesis of reduced graphene oxide-SiNW （rGO-SiNW） heterostructures to achieve greatly improved photocatalytic activity and stability. The SiNWs were synthesized through a metal-assisted electroless etching process and functionalized with reduced graphene oxide （rGO） flakes through a chemical absorption process. Here, the rGO not only functions as a physical protection layer to isolate the SiNWs from the harsh electrochemical environment but also serves as a charge mediator to facilitate the charge separation and transport processes. Furthermore, the rGO may also function as a redox catalyst to ensure efficient utilization of photo-carriers for the desired chemical reactions. Photocatalytic dye degradation studies show that the photoactivity of the heterostructures can be significantly enhanced with an initial activation process and maintained without apparent decay over repeated reaction cycles. Electrochemical and photo- electrochemical studies indicate that the enhanced photoactivity and photostability can be attributed to the more efficient separation of photoexcited charge carriers in SiNWs and the reduced self-oxidation of the surface of the SiNWs during the photocatalytic dye degradation process. The ability to significantly improve the photocatalytic activity and stability in rGO-SiNW heterostructures can not only lead to more opportunities for the application of silicon-based photocatalysts/ photoelectrodes for solar energy harvesting but also provide new insights into the stabilization of other unstable photocatalytic

关键词： graphene,silicon nanowire,photocatalyst,photoactivity,stability

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Optical characteristics of self-trapped excitons in 2D (iso-BA)_(2)PbI_(4) perovskite crystals

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Photonics Research 2022年第2期10卷 594-600页

作者： Haolin li Xuanyu Zhang Haizhen Wang Jiahao Yu Kexue li Zhipeng Wei dehui li Rui Chen State Key Laboratory of High Power Semiconductor Laser School of ScienceChangchun University of Science and TechnologyChangchun 130022China Department of Electrical and Electronic Engineering Southern University of Science and TechnologyShenzhen 518055China School of Optical and Electronic Information and Wuhan National Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430074China

Organic–inorganic halide metal perovskites are an exciting class of two-dimensional(2D) materials that have sparked renewed interest for next-generation optoelectronics. In particular, the self-trapped excitons(STEs)in 2D perovskite with excellent optical properties suggest great potential in display and narrowband detection.A prerequisite of understanding STEs’ properties is correct identification of the underlying interaction that leads to STEs. Here, the optical properties of STEs in(iso-BA)_(2)PbI_(4) are characterized through laser spectroscopy at various temperatures and excitation intensities. It is found that STEs are related to the octahedral distortion caused by strong electron–phonon interaction. Trapping and detrapping between STEs and free excitons(FEs) are clearly observed. With the increase in temperature, STEs and FEs will gain enough energy and migrate to each other. Moreover, by characterizing the thickness-dependent and two-photon excitation emission, it is confirmed that STEs exist inside the material because of their weak absorption. Our findings are of great significance for not only the fundamental understanding of STEs, but also the design and optimization of 2D-perovskite-based electronic and optoelectronic devices.

关键词： interaction perovskite excitation

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A field-effect approach to directly profiling the localized states in monolayer MoS2

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Science Bulletin 2019年第15期64卷 1049-1055页

作者： Hao Wu Yuan liu Zeyu Deng Hung-Chieh Cheng dehui li Jian Guo Qiyuan He Sen Yang Mengning Ding Yun-Chiao Huang Chen Wang Yu Huang Xiangfeng Duan Department of Materials Science and Engineering University of CaliforniaLos AngelesCA90095USA Department of Chemistry and Biochemistry University of CaliforniaLos AngelesCA90095USA California NanoSystems Institute University of CaliforniaLos AngelesCA90095USA

A fundamental understanding of the charge transport mechanism in two-dimensional semiconductors(e.g., MoS2) is crucial for fully exploring their potential in electronic and optoelectronic devices. By using monolayer graphene as the barrier-free contact to MoS2, we show that the field-modulated conductivity can be used to probe the electronic structure of the localized states. A series of regularly distributed plateaus were observed in the gate-dependent transfer curves. Calculations based on the variable-range hopping theory indicate that such plateaus can be attributed to the discrete localized states near mobility edge. This method provides an effective approach to directly profiling the localized states in conduction channel with an ultrahigh resolution up to 1 meV.

关键词： Two-dimensional layered materials Field-effect transistor Localized states Electronic transport Conductivity plateau

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Circularly polarized light emission and detection by chiral inorganic semiconductors

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Frontiers of Optoelectronics 2024年第2期17卷 43-49页

作者： Zha li Wancai li dehui li Wei Tang Huageng liang Huaibing Song Chao Chen liang Gao Jiang Tang Wuhan National Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430074China School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China International Health Care Center National Center for Global Health and MedicineTokyo 162‑8655Japan Hepato‑Biliary‑Pancreatic Surgery Division Department of SurgeryThe University of Tokyo HospitalTokyo 113‑8655Japan Department of Urology Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430074China Faculty of Materials Science and Chemistry China University of GeosciencesWuhan 430074China

Chiral inorganic semiconductors with high dissymmetric factor are highly desirable,but it is generally difficult to induce chiral structure in inorganic semiconductors because of their structure rigidity and *** this study,we introduced chiral ZnO film as hard template to transfer chirality to CsPbBr_(3) film and PbS quantum dots(QDs)for circularly polarized light(CPL)emission and detection,*** prepared CsPbBr_(3)/ZnO thin film exhibited CPL emission at 520 nm and the PbS QDs/ZnO film realized CPL detection at 780 nm,featuring high dissymmetric factor up to around *** electron transition based mechanism is responsible for chirality transfer.

关键词： High dissymmetric factor Circularly polarized light emission Semiconductor Hard template,Chirality

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