Oxygen adsorption and its influence on the thermoelectric performance of polycrystalline SnSe
Oxygen adsorption and its influence on the thermoelectric performance of polycrystalline SnSe
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氧吸附及其对多晶 SnSe 热电性能的影响
DOI：
10.1039/c9tc03999f
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发表时间：
2019
影响因子：
6.4
通讯作者：
Zhao Li-Dong
中科院分区：
文献类型：
--
作者：
Zhang Mengmeng;Wang Dongyang;Chang Cheng;Lin Tao;Wang Kedong;Zhao Li-Dong
SnSe是一种无毒且储量丰富的热电材料，由于SnSe晶体具有很高的热电性能而引起了广泛的关注。然而，这只能在正确合成和处理的单晶样品中观察到。本文首次利用扫描透射显微镜和光谱学技术，通过实验揭示了n型SnSe多晶样品性能不佳的原因。被吸附的氧被确定为类空穴受体，因为由于氧的电负性大，电子被氧捕获。通过抑制氧吸附，优化载流子浓度，使n型SnSe在773 K时的ZT最大值由0.3提高到~ 1.0。在了解了氧对热电性能的影响后，在发现氧是原因后，我们进一步提出了一种解决方案，即分别合金化具有较大和较小电负性的同系物S和Te。SnSe与Te合金的功率因数优于SnSe与S合金，进一步证实了添加剂的电负性对SnSe电输运性质的影响。结果表明，在制备多晶热电材料时，必须考虑氧效应。
SnSe, a nontoxic and earth-abundant thermoelectric material, has stimulated wide attention since the SnSe crystals were reported to exhibit high promising thermoelectric performances. However, this can be observed only for properly synthesized and handled single crystal samples. Here, we experimentally revealed the origin of the poor performance of an n-type polycrystalline SnSe sample by employing scanning transmission microscopy and spectroscopy for the first time. The adsorbed oxygen was identified as a hole-like acceptor because electrons were captured by oxygen due to its large electronegativity. The maximum ZT value of n-type SnSe was promoted from 0.3 to ∼1.0 at 773 K by optimizing carrier concentration via preventing oxygen adsorption. With the knowledge of the oxygen effects on thermoelectric performance and after finding that oxygen is the reason, we further provided a solution by alloying congeners S and Te having larger and smaller electronegativities, respectively. The power factor of SnSe alloyed with Te was superior to that of SnSe alloyed with S, which further confirmed the impact of the additive's electronegativity on the electrical transport properties of SnSe. Our results elucidate that oxygen effects must be taken into consideration when preparing polycrystalline thermoelectric materials.