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Enhancement of Thermoelectric Performances in a Topological Crystal Insulator Pb0.7Sn0.3Se via Weak Perturbation of the Topological State and Chemical Potential Tuning by Chlorine Doping
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2018-03-13 00:00:00 , DOI: 10.1021/acsami.8b00571 Chan-Chieh Lin 1 , Gareoung Kim 1 , Dianta Ginting 1, 2 , Kyunghan Ahn 1 , Jong-Soo Rhyee 1
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2018-03-13 00:00:00 , DOI: 10.1021/acsami.8b00571 Chan-Chieh Lin 1 , Gareoung Kim 1 , Dianta Ginting 1, 2 , Kyunghan Ahn 1 , Jong-Soo Rhyee 1
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Topological insulators generally share commonalities with good thermoelectric (TE) materials because of their narrow band gaps and heavy constituent elements. Here, we propose that a topological crystalline insulator (TCI) could exhibit a high TE performance by breaking its crystalline symmetry and tuning the chemical potential by elemental doping. As a candidate material, we investigate the TE properties of the Cl-doped TCI Pb0.7Sn0.3Se. The infrared absorption spectra reveal that the band gap is increased from 0.055 eV for Pb0.7Sn0.3Se to 0.075 eV for Pb0.7Sn0.3Se0.99Cl0.01, confirming that the Cl doping can break the crystalline mirror symmetry of a TCI Pb0.7Sn0.3Se and thereby enlarge its bulk electronic band gap. The topological band inversion is confirmed by the extended X-ray absorption fine structure spectroscopy, which shows that the TCI state is weakened in a chlorine x = 0.05-doped compound. The small gap opening and partial linear band dispersion with massless and massive bands may have a high power factor (PF) for high electrical conductivity with an enhancement of the Seebeck coefficient. As a result, Pb0.7Sn0.3Se0.99Cl0.01 shows a considerably enhanced ZT of 0.64 at 823 K, which is about 1200% enhancement in ZT compared with that of the undoped Pb0.7Sn0.3Se. This work demonstrates that the optimal n-type Cl doping tunes the chemical potential together with breaking the state of the TCI, suppresses the bipolar conduction at high temperatures, and thereby enables the Seebeck coefficient to increase up to 823 K, resulting in a significantly enhanced PF at high temperatures. In addition, the bipolar contribution to thermal conductivity is effectively suppressed for the Cl-doped samples of Pb0.7Sn0.3Se1–xClx (x ≥ 0.01). We propose that breaking the crystalline mirror symmetry in TCIs could be a new research direction for exploring high-performance TE materials.
中文翻译：
通过拓扑状态的微扰和通过氯掺杂调节化学势来增强拓扑晶体绝缘体Pb 0.7 Sn 0.3 Se中的热电性能
拓扑绝缘体通常具有良好的热电（TE）材料，因为它们的带隙窄且构成元素重，因此具有相同的共性。在这里，我们建议拓扑晶体绝缘体（TCI）可以通过打破其晶体对称性并通过元素掺杂来调节化学势来表现出较高的TE性能。作为候选材料，我们研究了掺Cl的TCI Pb 0.7 Sn 0.3 Se的TE特性。红外吸收光谱表明，带隙从Pb 0.7 Sn 0.3 Se的0.055 eV增加到Pb 0.7 Sn 0.3 Se 0.99 Cl 0.01的0.075 eV，证实了Cl掺杂可以破坏TCI Pb 0.7 Sn 0.3 Se的晶体镜对称性，从而扩大其体电子带隙。扩展的X射线吸收精细结构光谱证实了拓扑带反转，这表明在氯x = 0.05掺杂的化合物中，TCI状态减弱了。具有无质量带和质量带的小间隙开口和部分线性带分散可具有高功率因数（PF），以实现高电导率并提高塞贝克系数。结果，Pb 0.7 Sn 0.3 Se 0.99 Cl 0.01表现出显着增强的ZT在823 K时为0.64，比未掺杂的Pb 0.7 Sn 0.3 Se的ZT提高约1200％。这项工作表明，最佳的n型Cl掺杂可调节化学势，同时破坏TCI的状态，抑制高温下的双极传导，从而使塞贝克系数增加到823 K，从而显着提高PF在高温下。此外，对于掺Cl的Pb 0.7 Sn 0.3 Se 1– x Cl x（x≥0.01）。我们认为打破TCIs中的晶体镜对称性可能是探索高性能TE材料的新研究方向。
更新日期：2018-03-13
中文翻译：
通过拓扑状态的微扰和通过氯掺杂调节化学势来增强拓扑晶体绝缘体Pb 0.7 Sn 0.3 Se中的热电性能
拓扑绝缘体通常具有良好的热电（TE）材料，因为它们的带隙窄且构成元素重，因此具有相同的共性。在这里，我们建议拓扑晶体绝缘体（TCI）可以通过打破其晶体对称性并通过元素掺杂来调节化学势来表现出较高的TE性能。作为候选材料，我们研究了掺Cl的TCI Pb 0.7 Sn 0.3 Se的TE特性。红外吸收光谱表明，带隙从Pb 0.7 Sn 0.3 Se的0.055 eV增加到Pb 0.7 Sn 0.3 Se 0.99 Cl 0.01的0.075 eV，证实了Cl掺杂可以破坏TCI Pb 0.7 Sn 0.3 Se的晶体镜对称性，从而扩大其体电子带隙。扩展的X射线吸收精细结构光谱证实了拓扑带反转，这表明在氯x = 0.05掺杂的化合物中，TCI状态减弱了。具有无质量带和质量带的小间隙开口和部分线性带分散可具有高功率因数（PF），以实现高电导率并提高塞贝克系数。结果，Pb 0.7 Sn 0.3 Se 0.99 Cl 0.01表现出显着增强的ZT在823 K时为0.64，比未掺杂的Pb 0.7 Sn 0.3 Se的ZT提高约1200％。这项工作表明，最佳的n型Cl掺杂可调节化学势，同时破坏TCI的状态，抑制高温下的双极传导，从而使塞贝克系数增加到823 K，从而显着提高PF在高温下。此外，对于掺Cl的Pb 0.7 Sn 0.3 Se 1– x Cl x（x≥0.01）。我们认为打破TCIs中的晶体镜对称性可能是探索高性能TE材料的新研究方向。
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