缺陷调控提升□xCu2SnSe4(0≤x≤1)基热电性能的研究

Developing new materials and band engineering have obtained remarkable achievements for enhancement of thermoelectric performance, which utilizing special crystal structure to reduce the lattice thermal conductivity and increasing electrical properties of materials, respectively. Combination of these two strategies is a promising approach to enhance the thermoelectric performance. In this study, develop new thermoelectric materials with controllable and intrinsic vacancy structure was proposed. In these materials, the intrinsic vacancies can induce phonon scattering centers to reduce lattice thermal conductivity. Additionally, the concentration of the intrinsic vacancies in these materials can be tuned in a large scale, which makes the electrical properties increased simultaneously by the band engineering. Therefore, the thermoelectric performance of the materials with intrinsic vacancy structure can be improved by collaborative optimization of thermal properties and electrical properties. This project focuses on studying the thermoelectric performance of □xCu2SnSe4（□:vacancy, 0≤x≤1）compounds. The effect of vacancy in electron and phonon transport will be investigated to clarify the mechanism of the vacancy contribution in the thermoelectric performance. The effect of the different vacancy concentration in the band structure and electrical properties will be investigated to understand their key band parameter as thermoelectric performance enhancement and the direction of band optimization in these compounds. Thermoelectric performance of these compounds enhanced by collaborative optimization of thermal properties and electrical properties provides both of theoretic and empirical evidence for developing new thermoelectric materials with intrinsic vacancy.

新材料的开发和能带调控技术在提升材料热电性能研究方面已取得显著成效。新材料研究的主要出发点是利用特殊晶体结构基元降低晶格热导率；而能带调控的主要出发点是提升电学性能。有机结合这类策略是提升材料热电性能的有效途径。本研究提出晶体结构缺陷可调的热电新材料设计思路：利用缺陷引入声子散射中心，降低材料的晶格热导率；同时利用缺陷浓度在大范围可调的特点，实现能带结构调控提升电学性能，在同一材料中实现电性能与热性能的协同优化。本项目研究□xCu2SnSe4（□:晶格空位,0≤x≤1）基化合物热电性能，研究缺陷对电子和声子输运的影响，阐明缺陷结构对热电性能的作用机制；研究不同缺陷组分对能带结构及电学性能的影响，阐明提升该类材料热电性能的关键能带参数及其优化发展方向和能带调控技术；实现电性能和热性能的协同优化提升该类材料的热电性能，为具有本征缺陷结构的新型热电材料的开发提供理论和实验依据。

本项目在热输运性能方面，以缺位结构散射声子降低晶格热导率的设计思路，开发了具有本征缺位结构的新型高性能热电材料Cu2SnSe4。(1)通过优化制备工艺，获得高致密度的单相Cu2SnSe4材料。通过Cu的含量调控，实现宽范围空位浓度和载流子浓度可调，研究不同空位浓度和载流子浓度Cu2SnSe4基材料的塞贝克系数、电导率、热导率、载流子浓度及带隙宽度，建立了化学组分/空位浓度/载流子浓度与电-热性能之间的定量化评价模型，明确提升材料热电性能的关键参量及其调控技术，获得高性能Cu2±δSnSe4热电材料。此外，(2)从声子行进速率为出发点，提出了低声速低晶格热导率的设计思路，开发了具有本征低声速及超低晶格热导率的新型高性能热电材料Ag8SnSe6。在电输运性能方面，(3)以能带嵌套增加能带简并度的设计思路为指导，开发了在300700K温区内具有高性能的新型元素半导体热电材料Te，该研究填补了该温区内高性能元素半导体热电材料的空白。此外，(4)以能带汇聚增加能带简并度的设计思路为指导，通过在SnTe中固溶MnTe减小L与Σ价带间的能差来增加能带简并度，提升材料的电输运性能，获得高热电性能SnTe基固溶体材料。基于上述研究发表论文14篇，以第一/通讯作者在Nature Communication, Advanced Science和Chemistry of Materials等杂志发表论文4篇，其中ESI论文1篇。本项目研究成果为新型高性能热电材料的开发提供新的思路。