A Strategy to Suppress Phonon Transport in Molecular Junctions Using π-Stacked Systems
A Strategy to Suppress Phonon Transport in Molecular Junctions Using π-Stacked Systems
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DOI：
10.1021/acs.jpcc.7b02005
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发表时间：
2017-04-06
影响因子：
3.7
通讯作者：
Solomon, Gemma C.
中科院分区：
文献类型：
--
作者：
Li, Qian;Strange, Mikkel;Solomon, Gemma C.
分子结由于具有调节电子和热输运性质的潜力，是热电器件的有希望的候选者。然而，如果不降低声子对热导的贡献，就很难获得高的性能。在这里，我们提出了一种策略，以抑制声子传输在石墨烯为基础的分子结保持高电子功率因数，使用非键pi堆叠系统。利用第一性原理计算，我们发现与共价键分子结相比，pi堆叠系统的热导率可以降低约95%。π堆叠系统的声子传输在整个频率范围内衰减很大，剩余的传输主要发生在5太赫兹以下，其中面外通道占主导地位。由于极低的声子热导，pi堆叠分子结的优点系数（ZT）显著提高，为进一步优化电子性能留下了空间。
Molecular junctions are promising candidates for thermoelectric devices due to the potential to tune the electronic and thermal transport properties. However, a high figure of merit is hard to achieve, without reducing the phononic contribution to thermal conductance. Here, we propose a strategy to suppress phonon transport in graphene-based molecular junctions preserving high electronic power factor, using nonbonded pi-stackal systems. Using first-principles calculations, we find that the thermal conductance of pi-stacked systems can be reduced by about 95%, compared with that of a covalently bonded molecular junction. Phonon transmission of pi-stacked systems is largely attenuated in the whole frequency range, and the remaining transmission occurs mainly below 5 THz, where out-of-plane channels dominate. The figure of merit (ZT) of the pi-stacked molecular junction is dramatically enhanced because of the very low phononic thermal conductance, leaving tom for further optimization of the electronic properties.