Ultra-high average figure of merit in synergistic band engineered Sn Na1−Se0.9S0.1 single crystals
Ultra-high average figure of merit in synergistic band engineered Sn Na1−Se0.9S0.1 single crystals
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DOI：
10.1016/j.mattod.2017.11.005
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发表时间：
2018-06
期刊：
影响因子：
24.2
通讯作者：
Kunling Peng;Bin Zhang;Hong Wu;Xianlong Cao;Ang Li;Dingfeng Yang;Xu Lu;Guoyu Wang;Xiaodong Han;C. Uher;Xiaoyuan Zhou
中科院分区：
文献类型：
--
作者：
Kunling Peng;Bin Zhang;Hong Wu;Xianlong Cao;Ang Li;Dingfeng Yang;Xu Lu;Guoyu Wang;Xiaodong Han;C. Uher;Xiaoyuan Zhou
热电转换是收集热量并将其转换为易于储存和输送的电能的最有前途的途径之一。SignifiCan自1821年发现塞贝克效应以来一直没有取得任何进展，特别是在2014年，优值系数zT接近2.6%的创纪录高值。然而，对于热电器件，在工作温度范围内的高平均zT值(ZT Ave)更为重要，因为它直接关系到转换效率(η)。在过去的一个世纪里，为无Te材料实现高度稳定和可重复的超高zT Ave一直是一个历史性的挑战，尽管最近取得了令人兴奋的进展，ZT Ave远高于1.10。在这里，我们通过对SnSe单晶的协同能带工程策略，报道了一系列在宽温度范围内的创纪录的高zT平均值，在300 K到923K的范围内，在Na掺杂的SnSe 0.9 S 0.1固溶体单晶中接近∼1.60，在773K时最大zT为2.3。这些超高的热电性能源于SnSe 0.9 S 0.1中靠近能带边缘的新的多价带极值和通过Na掺杂引入额外的载流子口袋参与电输运而导致的费米能级向多谷带的移动。这些效应使Sn0.97Na0.03Se0.9S 0.1单晶的超高功率因数超过4 mW m−1K−2In Sn0 97Na0 0 3Se0 9 S 0 1。结合本征非谐性和点缺陷声子散射所导致的极低的热导率，探讨了超高zT AVE系列和在宽温度范围内创纪录的21%的转换效率。
Thermal-electricity conversion is one of the most promising routes to harvest heat and convert it as easily storable and deliverable electric energy. Significant progress has been made since the discovery of Seebeck effect in 1821, particularly, the figure of merit zT approached a record high value of 2.6 in 2014. However, for thermoelectric devices, high average zT values (zT ave) over the operating temperature range is more important as it is directly related to the conversion efficiency (η). Approaching highly stable and repeatable ultra-high zT ave for Te-free materials has been historically challenging over the past century though exciting progress with zT ave well above 1.10 was made recently. Here, through synergistic band engineering strategy for single crystalline SnSe, we report a series of record high zT ave over a wide temperature range, approaching∼ 1.60 in the range from 300 K to 923 K in Na-doped SnSe 0.9 S 0.1 solid solution single crystals, with the maximum zT of 2.3 at 773 K. These ultra-high thermoelectric performance derive from the new multiple valence band extrema near the band edges in SnSe 0.9 S 0.1 and the shift of Fermi level towards the multi-valley bands through Na doping which introduce additional carrier pockets to attend electrical transport. These effects result in an optimized ultrahigh power factor exceeding 4.0 mW m− 1 K− 2 in Sn 0.97 Na 0.03 Se 0.9 S 0.1 single crystals. Combined with the extremely lowered thermal conductivity attributed from the intrinsic anharmonicity and point defect phonon scattering, the series of ultra-high zT ave and a record high calculated conversion efficiency of 21% over a wide temperature range are approached.