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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 Cu2S and Cu2Se are systematically studied through first-principles and Boltzmann transport theory. The dynamic stability of monolayer Cu2S and Cu2Se through elastic constants and phonon dispersions are verified. The results show that monolayer Cu2S and Cu2Se have small lattice constants, resulting in lower phonon vibration modes. Phonon transport calculations confirm that monolayer Cu2Se has lower lattice thermal conductivity (1.93 W/(m·K)) than Cu2S (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 Cu2Se. The band degeneracy effect at the valence band maximum (VBM) of monolayer Cu2S and Cu2Se 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 Cu2S (Cu2Se) under n-type doping about 1011 cm–2 is 2.8×104 S/m (4.5×104 S/m), obviously superior to its conductivity about 2.6×102 S/m (1.6×103 S/m) under p-type doping. At the optimum doping concentration for monolayer Cu2S (Cu2Se), the n-type power factor is 16.5 mW/(m·K2) (25.9 mW/(m·K2)), which is far higher than p-type doping 1.1 mW/m·K2 (6.6 mW/(m·K2)). Through the above results, the excellent figure of merit of monolayer Cu2S (Cu2Se) 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 Cu2S (Cu2Se) are comparable to those of many promising thermoelectric materials reported recently. Especially, the figure of merit of monolayer Cu2Se is larger than that of the well-known high-efficient thermoelectric monolayer SnSe (2.32). Therefore, monolayer Cu2S and Cu2Se are potential thermoelectric materials with excellent performances and good application prospects. These results provide the theoretical basis for the follow-up experiments to explore the practical applications of 2D thermoelectric semiconductor materials and provide an in-depth insight into the effect of phonon thermal transport on improvement of TE transport properties.
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Keywords:
- first-principles /
- conductivity /
- thermal conductivity /
- thermoelectric
[1] Yang J, Stabler F R 2009 J. Electron. Mater. 38 1245Google Scholar
[2] Sootsman J, Chung D Y, Kanatzidis M 2009 Angew. Chem. 48 8616Google Scholar
[3] Rowe D M 1986 Appl. Energy 24 139Google Scholar
[4] Sales B 2002 Science 295 1248Google Scholar
[5] Zhang X, Zhao L D 2015 J. Materiomics 1 92Google Scholar
[6] Naghavi S S, He J, Xia Y, Wolverton C 2018 Chem. Mater. 30 5639Google Scholar
[7] Sajjad M, Singh N, Sattar S, Wolf S D, Schwingenschlögl U 2019 ACS Appl. Energy Mater. 2 3004Google Scholar
[8] Huang H H, Xing G, Fan X, Singh D J, Zheng W T 2019 J. Mater. Chem. C 7 5094Google Scholar
[9] Wang Y, Gao Z, Zhou J 2019 E Low dimens. Syst. Nanostruct. 108 53Google Scholar
[10] Xu B, Xia Q, Zhang J, Ma S, Wang Y, Xu Q, Li J, Wang Y 2020 Comput. Mater. Sci. 177 109588Google Scholar
[11] Shafique A, Samad A, Shin Y H 2017 Phys. Chem. Chem. Phys. 19 20677Google Scholar
[12] Liu X, Zhang D, Wang H, Chen Y, Wang H, Ni Y 2021 Phys. Chem. Chem. Phys. 23 24039Google Scholar
[13] Heremans J P, Jovovic V, Toberer E S, Saramat A, Kurosaki K, Charoenphakdee A, Yamanaka S, Snyder G J 2008 Science 321 554Google Scholar
[14] Tan X, Shao H, Hu T, Liu G Q, Ren S F 2015 J. Phys. Condens. Matter 27 095501Google Scholar
[15] Pei Y, Wang H, Snyder G J. 2012 Adv. Mater. 24 6125Google Scholar
[16] Reshak A H, Khan S A 2014 J. Magn. Magn. Mater. 354 216Google Scholar
[17] Pei Y Z, Shi X Y, Lalonde A, Wang H, Chen L D, Snyder G J 2011 Nature 473 66Google Scholar
[18] Yu J, Li T, Nie G, Zhang B P, Sun Q 2019 Nanoscale 11 10306Google Scholar
[19] Liu W, Shi X, Hong M, Yang L, Moshwan R, Chen Z G, Zou J 2018 J. Mater. Chem. C 6 13225Google Scholar
[20] Kresse G, Furthmüller J 1996 Comput. Mater. Sci. 6 15Google Scholar
[21] Wang V, Xu N, Liu J C, Tang G, Geng W T 2021 Comput. Phys. Commun. 267 108033Google Scholar
[22] Kresse G, Joubert D 1999 Phys. Rev. B 59 1758
[23] Heyd J, Scuseria G E, Ernzerhof M 2006 J. Chem. Phys. 124 8207
[24] Madsen G K H, Carrete J, Verstraete M J 2018 Comput. Phys. Commun. 231 140Google Scholar
[25] Togo A, Oba F, Tanaka I 2008 Phys. Rev. B 78 1341
[26] Li W, Carrete J, Katcho N A, Mingo N 2014 Comput. Phys. Commun. 185 1747Google Scholar
[27] Li W, Mingo N, Lindsay L, Broido D A, Stewart D A, Katcho N A 2012 Phys. Rev. B 85 195436Google Scholar
[28] Chen X, Wang D, Liu X, Li L, Sanyal B 2020 J. Phys. Chem. Lett. 11 2925Google Scholar
[29] Born M, Huang K 1955 Am. J. Phys. 23 474
[30] Zhang F, Zhu B, Guo H, Qiu J, Zheng K, Chen X, Yu J 2021 Appl. Surf. Sci. 550 149230Google Scholar
[31] Gao Z, Tao F, Ren J 2018 Nanoscale 10 12997Google Scholar
[32] Zhu X L, Zhang J R, Zhou P, Xie W X, Wang G F, Tian B 2019 Nanoscale 11 19923Google Scholar
[33] Guo S D, Wang Y H 2017 J. Appl. Phys. 121 034302Google Scholar
[34] Peng B, Zhang H, Shao H, Xu Y, Ni G, Zhang R, Zhu H 2016 Phys. Rev. B 94 245420Google Scholar
[35] Zhang W, Zhang X Q, Liu L, Wang Z, Li Z G 2021 Chin. Phys. B 30 526
[36] Ziman J M 1963 International Series of Monographs on Physics (Oxford: Clarendon) p168
[37] Carrete J, Li W, Lindsay L, Broido D A, Gallego L J, Mingo N 2016 Mater. Res. Lett. 4 204Google Scholar
[38] Slack G A 1973 J. Phys. Chem. Solids 34 321Google Scholar
[39] Broido D A, Ward A, Mingo N 2005 Phys. Rev. B 72 014308Google Scholar
[40] Lv B, Hu X, Liu X, Zhang Z, Song J, Luo Z 2020 Phys. Chem. Chem. Phys. 22 17833Google Scholar
[41] Morelli D T, Heremans J P 2002 Appl. Phys. Lett. 81 5126Google Scholar
[42] Bolen E, Deligoz E, Ozisik H 2021 Solid State Commun. 327 114223Google Scholar
[43] Mohanta M K, Sarkar A D 2020 ACS Appl. Mater. 12 18123Google Scholar
[44] Peng B, Zhang H, Shao H, Xu K, Ni G, Li J, Zhu H, Soukoulis C M 2018 J. Mater. Chem. A 6 2018Google Scholar
[45] 王宁 2022 博士论文 (成都: 电子科技大学)
Wang N 2022 Ph. D Dissertation (Chengdu: University of Electronic Science and Technology of China) (in Chinese)
[46] Qiu P, Agne M T, Liu Y, Zhu Y, Chen H, Mao T, Yang J, Zhang W, Haile S M, Zeier W G, Janek J, Uher C, Shi X, Chen L, Snyder G J 2018 Nat. Commun. 9 2910Google Scholar
[47] Brown D R, Day T, Caillat T, Snyder G J 2013 J. Electron. Mater. 42 2014Google Scholar
[48] Miyatani S Y, Suzuki Y 1953 J. Phys. Soc. Jpn. 8 680Google Scholar
[49] Maassen J, Lundstrom M 2013 Appl. Phys. Lett. 102 093103Google Scholar
[50] Sun Z H, Yuan K P, Chang Z, Bi S P, Zhang X L, Tang D W 2020 Nanoscale 12 3330Google Scholar
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图 1 单层Cu原子和X (X = S, Se)原子晶体结构的俯视图(a)和侧视图(b), 蓝色大球体表示Cu原子, 黄色小球代表X (X = S, Se)原子
Figure 1. Top (a) and side (b) views of the crystal structure of monolayer Cu atoms and X (X = S, Se) atoms. Cu atoms are represented as blue large spheres and X (X = S, Se) atoms are represented as yellow small spheres.
图 4 (a) 单层Cu2X (X =S, Se)的晶格热导率随温度变化趋势; (b) 300 K下单层Cu2S和Cu2Se的晶格热导率随平均自由程分布; (c), (d)声子寿命随频率分布, (e), (f) 声子群速度随频率分布; (g), (h) Grüneisen常数随频率分布
Figure 4. (a) Lattice thermal conductivity as a function of the temperature; (b) lattice thermal conductivity of monolayer Cu2X (X = S, Se) as a function of the MFP at 300 K; (c), (d) phonon lifetime as a function of the phonon frequency; (e), (f) phonon group velocity as a function of the phonon frequency; (g), (h) the Grüneisen parameter as a function of the phonon frequency.
图 5 单层Cu2X (X = S, Se)的塞贝克系数((a), (b))、电导率((c), (d))、功率因数((e), (f))、热电优值((g), (h))与p型和n型掺杂下的载流子浓度的关系
Figure 5. Seebeck coefficient ((a), (b)), conductivity ((c), (d)), power factor ((e), (f)), ZT ((g), (h)) as a function of carrier concentration for p-type and n-type doping of monolayer Cu2X (X = S, Se).
表 1 晶格常数α、Cu—X (X = S, Se) 键长l、Cu—X (X = S, Se)—Cu键角 θ1、Cu—X (X = S , Se)—Cu扭转角θ2、弹性张量C11, C12和C66、带隙EPBE, EHSE06由PBE和HSE06泛函计算实现
Table 1. Lattice parameters α, Cu—X (X = S, Se) bond lengths l, Cu—X (X = S, Se)—Cu bond angle θ1 , Cu—X (X = S, Se)—Cu twist angle θ2, elastic tensor C11, C12 and C66, electron bandgap EPBE, EHSE06 computed by PBE and HSE06.
α/Å l/Å θ1/(°) θ2/(°) C11 (C22)/(N·m–1) C12/(N·m–1) C66/(N·m–1) EPBE/eV EHSE06/eV Cu2S 5.02 2.22 70.78 21.38 34.7 2.3 19.6 0.23 1.15 Cu2Se 4.99 2.36 66.16 22.08 37.2 7.8 17.5 0.16 1.05 表 2 室温下部分2D材料的平均声学支的德拜温度
$ {\varTheta }_{{\rm{D}}} $ 和晶格热导率κlTable 2. The Debye temperature
$ {\varTheta }_{{\rm{D}}} $ and lattice thermal conductivity$ {\kappa }_{{\rm{l}}} $ of following 2D materials at room temperature.表 3 单层Cu2X (X = S, Se)的弹性模量 C2D、载流子有效质量
$ {m}^{*} $ ($ {m}_{0} $ ), 形变势常数$ {E}_{{\rm{l}}} $ , 载流子迁移率 μ和弛豫时间 τTable 3. Elastic modulus C2D, effective mass
$ {m}^{*} $ ($ {m}_{0} $ ), deformation potential constant$ {E}_{{\rm{l}}} $ , carrier mobility μ and relaxation time τ of monolayer Cu2X (X = S, Se).Type C2D/( N·m–1) $ {m}^{*} $ ${E}_{{\rm{l}}}$/eV μ/(cm2·(V·s)–1) τ/(10–14 s) Cu2S h 34.7 8.0 1.68 4.1 1.9 e 0.15 2.1 7.4×103 63.1 Cu2Se h 37.2 6.5 0.8 29.3 10.8 e 0.2 1.56 8.1×103 92.1 -
[1] Yang J, Stabler F R 2009 J. Electron. Mater. 38 1245Google Scholar
[2] Sootsman J, Chung D Y, Kanatzidis M 2009 Angew. Chem. 48 8616Google Scholar
[3] Rowe D M 1986 Appl. Energy 24 139Google Scholar
[4] Sales B 2002 Science 295 1248Google Scholar
[5] Zhang X, Zhao L D 2015 J. Materiomics 1 92Google Scholar
[6] Naghavi S S, He J, Xia Y, Wolverton C 2018 Chem. Mater. 30 5639Google Scholar
[7] Sajjad M, Singh N, Sattar S, Wolf S D, Schwingenschlögl U 2019 ACS Appl. Energy Mater. 2 3004Google Scholar
[8] Huang H H, Xing G, Fan X, Singh D J, Zheng W T 2019 J. Mater. Chem. C 7 5094Google Scholar
[9] Wang Y, Gao Z, Zhou J 2019 E Low dimens. Syst. Nanostruct. 108 53Google Scholar
[10] Xu B, Xia Q, Zhang J, Ma S, Wang Y, Xu Q, Li J, Wang Y 2020 Comput. Mater. Sci. 177 109588Google Scholar
[11] Shafique A, Samad A, Shin Y H 2017 Phys. Chem. Chem. Phys. 19 20677Google Scholar
[12] Liu X, Zhang D, Wang H, Chen Y, Wang H, Ni Y 2021 Phys. Chem. Chem. Phys. 23 24039Google Scholar
[13] Heremans J P, Jovovic V, Toberer E S, Saramat A, Kurosaki K, Charoenphakdee A, Yamanaka S, Snyder G J 2008 Science 321 554Google Scholar
[14] Tan X, Shao H, Hu T, Liu G Q, Ren S F 2015 J. Phys. Condens. Matter 27 095501Google Scholar
[15] Pei Y, Wang H, Snyder G J. 2012 Adv. Mater. 24 6125Google Scholar
[16] Reshak A H, Khan S A 2014 J. Magn. Magn. Mater. 354 216Google Scholar
[17] Pei Y Z, Shi X Y, Lalonde A, Wang H, Chen L D, Snyder G J 2011 Nature 473 66Google Scholar
[18] Yu J, Li T, Nie G, Zhang B P, Sun Q 2019 Nanoscale 11 10306Google Scholar
[19] Liu W, Shi X, Hong M, Yang L, Moshwan R, Chen Z G, Zou J 2018 J. Mater. Chem. C 6 13225Google Scholar
[20] Kresse G, Furthmüller J 1996 Comput. Mater. Sci. 6 15Google Scholar
[21] Wang V, Xu N, Liu J C, Tang G, Geng W T 2021 Comput. Phys. Commun. 267 108033Google Scholar
[22] Kresse G, Joubert D 1999 Phys. Rev. B 59 1758
[23] Heyd J, Scuseria G E, Ernzerhof M 2006 J. Chem. Phys. 124 8207
[24] Madsen G K H, Carrete J, Verstraete M J 2018 Comput. Phys. Commun. 231 140Google Scholar
[25] Togo A, Oba F, Tanaka I 2008 Phys. Rev. B 78 1341
[26] Li W, Carrete J, Katcho N A, Mingo N 2014 Comput. Phys. Commun. 185 1747Google Scholar
[27] Li W, Mingo N, Lindsay L, Broido D A, Stewart D A, Katcho N A 2012 Phys. Rev. B 85 195436Google Scholar
[28] Chen X, Wang D, Liu X, Li L, Sanyal B 2020 J. Phys. Chem. Lett. 11 2925Google Scholar
[29] Born M, Huang K 1955 Am. J. Phys. 23 474
[30] Zhang F, Zhu B, Guo H, Qiu J, Zheng K, Chen X, Yu J 2021 Appl. Surf. Sci. 550 149230Google Scholar
[31] Gao Z, Tao F, Ren J 2018 Nanoscale 10 12997Google Scholar
[32] Zhu X L, Zhang J R, Zhou P, Xie W X, Wang G F, Tian B 2019 Nanoscale 11 19923Google Scholar
[33] Guo S D, Wang Y H 2017 J. Appl. Phys. 121 034302Google Scholar
[34] Peng B, Zhang H, Shao H, Xu Y, Ni G, Zhang R, Zhu H 2016 Phys. Rev. B 94 245420Google Scholar
[35] Zhang W, Zhang X Q, Liu L, Wang Z, Li Z G 2021 Chin. Phys. B 30 526
[36] Ziman J M 1963 International Series of Monographs on Physics (Oxford: Clarendon) p168
[37] Carrete J, Li W, Lindsay L, Broido D A, Gallego L J, Mingo N 2016 Mater. Res. Lett. 4 204Google Scholar
[38] Slack G A 1973 J. Phys. Chem. Solids 34 321Google Scholar
[39] Broido D A, Ward A, Mingo N 2005 Phys. Rev. B 72 014308Google Scholar
[40] Lv B, Hu X, Liu X, Zhang Z, Song J, Luo Z 2020 Phys. Chem. Chem. Phys. 22 17833Google Scholar
[41] Morelli D T, Heremans J P 2002 Appl. Phys. Lett. 81 5126Google Scholar
[42] Bolen E, Deligoz E, Ozisik H 2021 Solid State Commun. 327 114223Google Scholar
[43] Mohanta M K, Sarkar A D 2020 ACS Appl. Mater. 12 18123Google Scholar
[44] Peng B, Zhang H, Shao H, Xu K, Ni G, Li J, Zhu H, Soukoulis C M 2018 J. Mater. Chem. A 6 2018Google Scholar
[45] 王宁 2022 博士论文 (成都: 电子科技大学)
Wang N 2022 Ph. D Dissertation (Chengdu: University of Electronic Science and Technology of China) (in Chinese)
[46] Qiu P, Agne M T, Liu Y, Zhu Y, Chen H, Mao T, Yang J, Zhang W, Haile S M, Zeier W G, Janek J, Uher C, Shi X, Chen L, Snyder G J 2018 Nat. Commun. 9 2910Google Scholar
[47] Brown D R, Day T, Caillat T, Snyder G J 2013 J. Electron. Mater. 42 2014Google Scholar
[48] Miyatani S Y, Suzuki Y 1953 J. Phys. Soc. Jpn. 8 680Google Scholar
[49] Maassen J, Lundstrom M 2013 Appl. Phys. Lett. 102 093103Google Scholar
[50] Sun Z H, Yuan K P, Chang Z, Bi S P, Zhang X L, Tang D W 2020 Nanoscale 12 3330Google Scholar
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