Size‐ and Temperature‐Dependent Suppression of Phonon Thermal Conductivity in Carbon Nanotube Thermoelectric Films
Size‐ and Temperature‐Dependent Suppression of Phonon Thermal Conductivity in Carbon Nanotube Thermoelectric Films
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DOI：
10.1002/aelm.202000746
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发表时间：
2020-10
影响因子：
6.2
通讯作者：
D. Wesenberg;M. Roos;A. D. Avery;J. Blackburn;Andrew J. Ferguson;B. Zink
中科院分区：
文献类型：
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作者：
D. Wesenberg;M. Roos;A. D. Avery;J. Blackburn;Andrew J. Ferguson;B. Zink
碳纳米管和石墨烯等纳米级碳材料中的热传输通常由声子主导。在这里，测量了两个厚度为100 nm的单壁半导体碳纳米管薄膜在77-350K温度范围内的面内热导率、电导率和热功率。这些测量是在氮化硅薄膜隔热平台上进行的。这两个薄膜是由管子和管束大小不同的无序管网形成的，具有非常不同的导热系数。其中一种薄膜符合一个简单的热传导模型，假设声子速度和平均自由程恒定，德拜热容为3d，德拜温度为770K。第二种薄膜表现出更复杂的温度依赖关系，在200K附近的一个相对狭窄的窗口中，声子对热导率的贡献基本上消失。这导致在相同温度下热电优值相应地大幅增加。对这一行为的更好理解可以显著提高这些低成本、富含地球的有机电子材料的热电效率。室温附近的热导率和电荷电导率也是掺杂的函数，这为无序纳米管薄膜中掺杂分子的相互作用和声子输运提供了进一步的信息。
Heat transport in nanoscale carbon materials such as carbon nanotubes and graphene is normally dominated by phonons. Here, measurements of in‐plane thermal conductivity, electrical conductivity, and thermopower are presented from 77–350 K on two films with thickness <100 nm formed from semiconducting single‐walled carbon nanotubes. These measurements are made with silicon–nitride membrane thermal isolation platforms. The two films, formed from disordered networks of tubes with differing tube and bundle size, have very different thermal conductivity. One film matches a simple model of heat conduction assuming constant phonon velocity and mean free path, and 3D Debye heat capacity with a Debye temperature of 770 K. The second film shows a more complicated temperature dependence, with a dramatic drop in a relatively narrow window near 200 K where phonon contributions to thermal conductivity essentially vanish. This causes a corresponding large increase in thermoelectric figure‐of‐merit at the same temperature. A better understanding of this behavior can allow significant improvement in thermoelectric efficiency of these low‐cost earth‐abundant, organic electronic materials. Heat and charge conductivity near room temperature is also presented as a function of doping, which provides further information on the interaction of dopant molecules and phonon transport in disordered nanotube films.