单层Cu_(2)X的热电性质  

Thermoelectric properties of monolayer Cu_(2)X

作　　者：郑建军 张丽萍[1] Zheng Jian-Jun;Zhang Li-Ping(School of Materials and Physics,China University of Mining and Technology,Xuzhou 221116,China)

机构地区：[1]中国矿业大学材料与物理学院,徐州221116

出　　处：《物理学报》2023年第8期255-263,共9页Acta Physica Sinica

摘　　要：具有低晶格热导率和高热电优值的二维(2D)材料可用于热电器件的制备.本文通过第一性原理和玻尔兹曼输运理论,系统地预测了单层Cu_(2)X(X=S,Se)的热电性质.研究发现单层Cu_(2)Se较Cu_(2)S在室温下具有更低的晶格热导率(1.93 W/(m·K)和3.25 W/(m·K)),这源于其更低的德拜温度和更强的非谐性.单层Cu_(2)X(X=S,Se)价带顶处的能带简并效应显著增大了其载流子有效质量,导致p型掺杂下具有高的塞贝克系数和低的电导率.在最优掺杂浓度下,单层Cu_(2)S(Cu_(2)Se)n型的功率因数16.5 mW/(m·K^(2))(25.9 mW/(m·K^(2)))远高于其p型的功率因数1.1 mW/(m·K^(2))(6.6 mW/(m·K^(2))),且随着温度的提升这一优势将更加明显.温度为700 K时,单层Cu_(2)S和Cu_(2)Se在n型最优掺杂浓度下的热电优值可以达到1.85和2.82,高于p型最优掺杂浓度下的热电优值0.38和1.7.单层Cu_(2)X(X=S,Se)的优良热电性能可与近期报道的许多先进的热电材料相媲美,特别是单层Cu_(2)Se的热电优值高于众所周知的先进热电材料—单层SnSe(2.32).因此,单层Cu_(2)X(X=S,Se)是一类具有优异性能和良好应用前景的潜在热电材料.这些结果为后续探索2D热电材料的实验及应用提供了理论依据,并为深入了解声子热输运对热电优值的影响提供了新的见解.Two-dimensional(2D)materials with lower lattice thermal conductivities and high figures of merit are useful for applications in thermoelectric(TE)devices.In this work,the thermoelectric properties of monolayer Cu_(2)S and Cu_(2)Se are systematically studied through first-principles and Boltzmann transport theory.The dynamic stability of monolayer Cu_(2)S and Cu_(2)Se through elastic constants and phonon dispersions are verified.The results show that monolayer Cu_(2)S and Cu_(2)Se have small lattice constants,resulting in lower phonon vibration modes.Phonon transport calculations confirm that monolayer Cu_(2)Se has lower lattice thermal conductivity(1.93 W/(m·K))than Cu_(2)S(3.25 W/(m·K))at room temperature,which is due to its small Debye temperature and stronger anharmonicity.Moreover,the heavier atomic mass of Se atom effectively reduces the phonon frequency,resulting in an ultra narrow phonon band gap(0.08 THz)and a lower lattice thermal conductivity for monolayer Cu_(2)Se.The band degeneracy effect at the valence band maximum(VBM)of monolayer Cu_(2)S and Cu_(2)Se significantly increase their carrier effective mass,resulting in higher Seebeck coefficients and lower conductivities under p-type doping.The electric transport calculation at room temperature shows that the conductivity of monolayer Cu_(2)S(Cu_(2)Se)under n-type doping about 1011 cm–2 is 2.8×10^(4)S/m(4.5×10^(4)S/m),obviously superior to its conductivity about 2.6×10^(2)S/m(1.6×103 S/m)under p-type doping.At the optimum doping concentration for monolayer Cu_(2)S(Cu_(2)Se),the n-type power factor is 16.5 mW/(m·K^(2))(25.9 mW/(m·K^(2))),which is far higher than p-type doping 1.1 mW/m·K^(2)(6.6 mW/(m·K^(2))).Through the above results,the excellent figure of merit of monolayer Cu_(2)S(Cu_(2)Se)under optimal n-type doping at 700 K can approach to 1.85(2.82),which is higher than 0.38(1.7)under optimal p-type doping.The excellent thermoelectric properties of monolayer Cu_(2)S(Cu_(2)Se)are comparable to those of many promising thermoelectric mate

关 键 词：第一性原理 电导率 热导率 热电 

分 类 号：TB34[一般工业技术—材料科学与工程]