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phonon scattering and exciton localization: molding exciton flux in two dimensional disorder energy landscape

eLight 2021年第1期1卷 57-68页

作者： Pengfei Qi Yang Luo Beibei Shi Wei Li Donglin Liu Liheng Zheng Zhixin Liu Yanglong Hou Zheyu Fang School of Physics State Key Laboratory for Mesoscopic PhysicsAcademy for Advanced Interdisciplinary StudiesCollaborative Innovation Center of Quantum MatterNano-Optoelectronics Frontier Center of Ministry of EducationPeking UniversityBeijing 100871China. Institute of Modern Optics Tianjin Key Laboratory of Micro-Scale Optical Information Science and TechnologyNankai UniversityTianjin 300350China. Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing Innovation Centre for Engineering Science and Advanced TechnologyDepartment of Materials Science and EngineeringCollege of EngineeringPeking UniversityBeijing 100871China.

Two dimensional excitonic devices are of great potential to overcome the dilemma of response time and integration in current generation of electron or/and photon based systems.The ultrashort diffusion length of exciton arising from ultrafast relaxation and low carrier mobility greatly discounts the performance of excitonic devices.phonon scattering and exciton localization are crucial to understand the modulation of exciton flux in two dimensional disorder energy landscape,which still remain elusive.Here,we report an optimized scheme for exciton diffusion and relaxation dominated by phonon scattering and disorder potentials in WSe2 monolayers.The effective diffusion coefficient is enhanced by>200%at 280 K.The excitons tend to be localized by disorder potentials accompanied by the steadily weakening of phonon scattering when temperature drops to 260 K,and the onset of exciton localization brings forward as decreasing temperature.These findings identify that phonon scattering and disorder potentials are of great importance for long-range exciton diffusion and thermal management in exciton based systems,and lay a firm foundation for the development of functional excitonic devices.

关键词： Exciton diffusion Exciton relaxation 2D semiconductors phonon scattering Disorder potentials

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Optimizing thermoelectric properties of BiSe through Cu additive enhanced effective mass and phonon scattering

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Rare Metals 2020年第12期39卷 1374-1382页

作者： Xing-Chen Shen Xiao Zhang Bin Zhang Guo-Yu Wang Jian He Xiao-Yuan Zhou Chongqing Key Laboratory of Soft Condensed Matter Physics and Smart Materials College of PhysicsChongqing UniversityChongqing 401331China Chongqing Institute of Green and Intelligent Technology Chinese Academy of ScienceChongqing 400714China Department of Physics and Astronomy Clemson UniversityClemsonSC29634USA Analytical and Testing Center of Chongqing University Chongqing401331China University of Chinese Academy of Sciences Beijing100044China

Known as a weak topological insulator(TI),BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer("Bi_(2)")and three-dimensional TI layer("Bi_(2)Se_(3)").The low lattice thermal conductivity of BiSe due to the presence of Bi2 bilayers promises potentially good thermoelectric performance.Herein,the thermoelectric properties of nominal Bi_(1-x)Cu_(x)Se samples were studied as the functions of the content of Cu additive and temperature.It is found that Cu additives in BiSe(1)profoundly affect the texture of densified polycrystalline samples by inclining the crystallographic c-axis parallel toward the pressure direction in the densification process,(2)increase considerably the effective mass and thus the Seebeck coefficient,and(3)yield point defects and Cu-Se secondary phases that effectively scatter heat-carrying phonons.As a result,the optimized electrical and thermal properties yield a thermoelectric figure of merit of zT~0.29 in Bi_(1-x)Cu_(x)Se(x=0.03)sample at 467 K in parallel to the pressure direction and a zT~0.20 at 468 K in the perpendicular direction.

关键词： Cu additives phonon scattering Effective mass Texture Thermoelectric

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Simultaneous optimization of phononic and electronic transport in two-dimensional Bi2O2Se by defect engineering

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Science China(Information Sciences) 2023年第6期66卷 87-93页

作者： Fang YANG Hong Kuan NG Jing WU Yunshan ZHAO Junpeng LU School of Physics Southeast University Institute of Materials Research and Engineering Agency for ScienceTechnology and Research NNU-SULI Thermal Energy Research Center (NSTER) & Center for Quantum Transport and Thermal Energy Science (CQTES) School of Physics and TechnologyNanjing Normal University

Defect engineering represents one degree of freedom to tune the physical and chemical properties of two-dimensional (2D)materials.Here,we demonstrate that the thermal and electronic properties of 2D Bi2O2Se can be optimized simultaneously by introducing oxygen defects.2D Bi2O2Se and its oxygendeficient counterpart (Bi2Ox Se,xscattering of phonons by targeting of high-,mid-,and low-frequency phonons due to oxygen defects,strong anharmonicity,and nanostructure boundaries,respectively.Meanwhile,the mobility is also improved to 260–500 cm2·V-1·s-1and the usual polar optical phonon scattering in 2D Bi2O2Se is weakened owing to the introduction of oxygen defects.Our results promise potential applications for thermoelectric design,nanoelectronics,and thermal barrier coating devices based on emerging 2D materials.

关键词： 2D Bi$_2$O$_2$Se thermal conductivity oxygens defects phonon scattering mobility

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Annealing engineering induced high thermoelectric performance in Yb-filled CoSb_(3) skutterudites

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Journal of Materials Science & Technology 2023年第19期150卷 168-174页

作者： Haoran Feng Qian Deng Yan Zhong Xuri Rao Yadong Wang Jianglong Zhu Fujie Zhang Ran Ang Key Laboratory of Radiation Physics and Technology Ministry of EducationInstitute of Nuclear Science and TechnologySichuan UniversityChengdu 610064China Institute of New Energy and Low-Carbon Technology Sichuan UniversityChengdu 610065China

The great pressure of energy shortage has made CoSb_(3) materials with excellent mechanical stability in the mid-temperature region favored for the integration of thermoelectric devices.However,their ex-cessive lattice thermal conductivity and poor Seebeck coefficient lead to low energy conversion effi-ciency.Filling Yb into the lattice void to optimize the band structure and regulate the chemical po-tential is an indispensable means for improving the thermoelectric properties of CoSb_(3)-based materials,while the phase structure and thermoelectric properties vary with the preparation process.This motivates the current work to focus on the influence of annealing temperature on the microstructure and thermoelectric properties of Yb-filled CoSb_(3).Experimental analysis and theoretical model eluci-dated that an increase in annealing temperature can optimize the Yb filling fraction,which simulta-neously manipulates the band structure as well as chemical potential,resulting in an excellent electrical property.Furthermore,the phase and microstructure characterization clarify that the annealing temperature can effectively affect the grain size.The complex grain boundary induced by grain refinement,more filled Yb atoms and precipitates strongly scatter wide-frequency phonons,significantly suppressing the lattice thermal conductivity.As a result,a superior dimensionless figure of merit(ZT)value of~1.33 at 823 K and an average ZTave of~0.9(323-823 K)were achieved in the Ybo.4Co4Sb12 sample annealed at 923 K,and the calculated conversion efficiency could reach~13%.This work pro-vides a unique paradigm to improve thermoelectrics in the filled CoSb_(3)-based skutterudites by annealing engineering.

关键词： CoSb_(3)skutterudite Annealing engineering Grain refinement phonon scattering Thermoelectric optimization

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Superior multiphase interfaces in AgCuTe-based composite with significantly enhanced thermoelectric properties

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先进陶瓷(英文) 2023年第8期12卷 1511-1520页

作者： Wenpei Li Zhonghai Yu Chengyan Liu Ying Peng Baoquan Feng Jie Gao Guojing Wu Xiaobo Bai Junliang Chen Xiaoyang Wang Lei Miao Guangxi Key Laboratory of Information Materials Electronical Information Materials and Devices Engineering Research Center of Ministry of EducationSchool of Materials Science and EngineeringGuilin University of Electronic TechnologyGuilin 541004China Guangxi Key Laboratory of Precision Navigation Technology and Application School of Information and CommunicationGuilin University of Electronic TechnologyGuilin 541004China

It is common sense that a phase interface(or grain boundary)could be used to scatter phonons in thermoelectric(TE)materials,resulting in low thermal conductivity(k).However,a large number of impurity phases are always so harmful to the transport of carriers that poor TE performance is obtained.Here,we demonstrate that numerous superior multiphase(AgCuTe,Ag_(−2)Te,copper telluride(Cu_(2)Te and Cu_(2−x)Te),and nickel telluride(NiTe))interfaces with simultaneous strong phonon scattering and weak electron scattering could be realized in AgCuTe-based TE materials.Owing to the similar chemical bonds in these phases,the depletion region at phase interfaces,which acts as carrier scattering centers,could be ignored.Therefore,the power factor(PF)is obviously enhanced from~609 to~832μW·m^(−1)·K^(−2),and k is simultaneously decreased from~0.52 to~0.43 W·m^(−1)·K^(−1) at 636 K.Finally,a peak figure of merit(zT)of~1.23 at 636 K and an average zT(zTavg)of~1.12 in the temperature range of 523–623 K are achieved,which are one of the best values among the AgCuTe-based TE materials.This study could provide new guidance to enhance the performance by designing superior multiphase interfaces in the TE materials.

关键词： thermoelectric(TE)materials AgCuTe phase interface carrier scattering phonon scattering

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Interfacial ion regulation on 2D layered double hydroxide nanosheets for enhanced thermal insulation

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Science China Chemistry 2022年第5期65卷 898-904页

作者： Chun Wang Hengyu Xu Han Cheng Hao Yu Si Liu Wenjie Wang Ruilin Yuan Hongfei Liu Tianpei Zhou Wangsheng Chu HengAn Wu Yi Xie Changzheng Wu Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaCAS Center for Excellence in Nanoscienceand CAS Key Laboratory of Mechanical Behavior and Design of MaterialsHefei 230026China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsCAS Center for Excellence in Complex System Mechanics University of Science and Technology of ChinaHefei 230027China National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China Institute of Energy Hefei Comprehensive National Science CenterHefei 230031China

Exploring new strategies to broaden the upper/lower limit of thermal conductivity is of great interest to develop thermal management materials that can adapt to extreme environments.In this work,we employ an interfacial ion regulation to enhance the thermal insulation performance of 2D layered double hydroxide nanosheets.The introduction of interfacial ion enlarges the interplanar spacing of Co(OH)_(2) nanosheets from 4.64 to 8.05 ?,which reduces phonon scattering length perpendicular to the two-dimensional plane and leads to enhanced interlayer thermal insulation.The interfacial ion-regulated Co(OH)_(2)(named as Co(OH)_(2)-M^(x-)) exhibits 3-fold enhancement of thermal insulation through decreasing the thermal conductivity to as low as 0.15 W m^(-1) K^(-1),which is among the top values in 2D solid materials.We anticipate that interfacial ion regulation for 2D nanosheets paves a new avenue to break through the thermal insulation limit.

关键词： two dimensional materials interfacial ion regulation thermal conductivity phonon scattering

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Lattice thermal conduction in cadmium arsenide

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Chinese Physics B 2022年第11期31卷 424-430页

作者： R F Chinnappagoudra M D Kamatagi N R Patil N S Sankeshwar Department of Physics S.S.Government First Grade CollegeNargund-582207KarnatakaIndia Research Resource Centre Visvesvaraya Technological UniversityBelagavi-590018KarnatakIndia Department of Physics B V B College of Engineering and TechnologyHubliKarnataka 80031India Department of Physics&Electronics CHRIST(Deemed to be University)Bangalore-560029KarnatakaIndia

Lattice thermal conductivity(LTC)of cadmium arsenide(Cd_(3)As_(2))is studied over a wide temperature range(1–400 K)by employing the Callaway model.The acoustic phonons are considered to be the major carriers of heat and to be scattered by the sample boundaries,disorder,impurities,and other phonons via both Umklapp and normal phonon processes.Numerical calculations of LTC of Cd_(3)As_(2)bring out the relative importance of the scattering mechanisms.Our systematic analysis of recent experimental data on thermal conductivity(TC)of Cd_(3)As_(2)samples of different groups,presented in terms of LTC,κL,using a nonlinear regression method,reveals good fits to the TC data of the samples considered for T100 K the inclusion of the electronic component of TC,κe,incorporating contributions from relevant electron scattering mechanisms,is needed to obtain good agreement with the TC data over the wide temperature range.More detailed investigations of TC of Cd_(3)As_(2)are required to better understand its suitability in thermoelectric and thermal management devices.

关键词： dirac semimetals Cd_(3)As_(2) thermal conductivity phonon scattering

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Realizing high thermoelectric performance for p-type SiGe in medium temperature region via TaC compositing

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Journal of Materiomics 2023年第5期9卷 984-991页

作者： Zheng Fan JiSheng Liang Jun-Liang Chen Ying Peng Huajun Lai Jian Nong Chengyan Liu Wangyang Ding Lei Miao Guangxi Key Laboratory for Relativity Astrophysics State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite StructuresSchool of Physical Science and TechnologyGuangxi UniversityNanning530004China Engineering Research Center of Electronic Information Materials and Devices Ministry of EducationGuangxi Key Laboratory of Information MaterialGuilin University of Electronic TechnologyGuilin541004China Guangxi Key Laboratory of Precision Navigation Technology and Application Guilin University of Electronic TechnologyGuilin541004China Guangxi Academy of Sciences Nanning530007China

SiGe is recognised as an excellent thermoelectric material with superior mechanical properties and thermal stability in regions with high temperatures.This study explores a novel strategy for coregulating thermoelectric transport parameters to achieve high thermoelectric properties of p-type SiGe in the mid-temperature region by incorporating nano-TaC into SiGe combined ball milling with spark plasma sintering.By optimizing the amount of TaC in the SiGe matrix,the power factors were significantly increased due to the modulation doping effect based on the work function matching of SiGe with TaC.Simultaneously,the ensemble effect of the nanostructure leads to a significant decrease in thermal conductivity.Thus,a high ZT of 1.06 was accomplished at 873 K,which is 64%higher than that of typical radioisotope thermoelectric generator.Our research offers a novel strategy for expanding and enhancing the thermoelectric properties of SiGe materials in the medium temperature range.

关键词： SiGe Thermoelectric Work function matching Modulation doping effect phonon scattering

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Tuning the thermal conductivity of strontium titanate through annealing treatments

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Chinese Physics B 2017年第1期26卷 357-362页

作者：张喨李宁王惠琼张宇锋任飞廖霞霞李亚平王小丹黄政戴扬鄢浩郑金成 Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices Department of PhysicsXiamen University Xiamen University Malaysia Department of Chemical Engineering School of Environmental and Chemical EngineeringShanghai University Fujian Provincial Key Laboratory of Mathematical Modeling and High-Performance Scientific Computation

Strontium titanate（SrTiO3） is a promising n-type material for thermoelectric applications. However, its relatively high thermal conductivity limits its performance in efficiently converting heat into electrical power through thermoelectric effect.This work shows that the thermal conductivity of SrTiO3 can be effectively reduced by annealing treatments, through an integrated study of laser flash measurement, scanning electron microscopy, Fourier transform infrared spectroscopy, x-ray absorption fine structure, and first-principles calculations. A phonon scattering model is proposed to explain the reduction of thermal conductivity after annealing. This work suggests a promising means to characterize and optimize the material for thermoelectric applications.

关键词： thermal conductivity SrTiO3 annealing phonon scattering

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Point Defect Engineering Boosting the Thermoelectric Properties of Layered 122 Zintl Compounds

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Chinese Journal of Structural Chemistry 2020年第5期39卷 815-820页

作者： GUO Kai HUO Hao-Jie LUO Jun School of Materials Science and Engineering Shanghai UniversityShanghai 200444China Materials Genome Institute Shanghai UniversityShanghai 200444China

The layered 122 Zintl compounds have become an intriguing class of thermoelectric materials due to the promising electronic transport properties and inherently low thermal conductivity,showing the typical characteristics of"phonon-glass electron-crystal".Owing to the unprecedented performance tunability,the thermoelectric properties of the layered-structure compounds are completive with some traditional thermoelectric materials.Point defects involving vacancy,aliovalent doping and equivalent alloying atoms have been introduced to further enhance the thermoelectric properties.This review emphasizes the effects of various point defects on the thermoelectric parameters,and provides perspective on the strategies for increasing the thermoelectric figure of merit zT,which are believed to be applicable for improving the thermoelectric properties of many other compounds.

关键词： layered structure 122 Zintl phase point defect orbital alignment phonon scattering thermoelectric properties

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