Lead‐free tin sulfide (SnS), with an analogous structure to SnSe, has attracted increasing attention because of its theoretically predicted high thermoelectric performance. In practice, however, polycrystalline SnS performs rather poorly as a result of its low power factor. In this work, bulk sodium (Na)‐doped SnS single crystals are synthesized using a modified Bridgman method and a detailed transport evaluation is conducted. The highest zT value of ≈1.1 is reached at 870 K in a 2 at% Na‐doped SnS single crystal along the b‐axis direction, in which high power factors (2.0 mW m⁻¹ K⁻² at room temperature) are realized. These high power factors are attributed to the high mobility associated with the single crystalline nature of the samples as well as to the enhanced carrier concentration achieved through Na doping. An effective single parabolic band model coupled with first‐principles calculations is used to provide theoretical insight into the electronic transport properties. This work demonstrates that SnS‐based single crystals composed of earth‐abundant, low‐cost, and nontoxic chemical elements can exhibit high thermoelectric performance and thus hold potential for application in the area of waste heat recovery.

中文翻译：

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钠掺杂的硫化锡单晶：具有高热电性能的无毒的富含地球的材料

与SnSe类似的无铅硫化锡（SnS），由于其理论上预测的高热电性能而受到越来越多的关注。然而，实际上，由于其低功率因数，多晶SnS的性能相当差。在这项工作中，使用改良的Bridgman方法合成了掺有钠（Na）的大块SnS单晶，并进行了详细的传输评估。沿着b轴方向，在2at％的Na掺杂SnS单晶中，在870 K时达到了最高的zT值≈1.1 ，其中高功率因数（2.0 mW m ^-1 K ^-2在室温下）。这些高功率因数归因于与样品的单晶性质相关的高迁移率，以及归因于通过Na掺杂获得的提高的载流子浓度。有效的单抛物线能带模型与第一性原理计算相结合，可为电子传输特性提供理论上的见识。这项工作表明，由富含地球，低成本和无毒化学元素组成的SnS基单晶可以表现出较高的热电性能，因此在废热回收领域具有应用潜力。