能带非对称性改造提升热电性能的研究

项目名称： 能带非对称性改造提升热电性能的研究

项目编号： No.11474219

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 裴艳中

作者单位： 同济大学

项目金额： 88万元

中文摘要： 能带调控是提升热电性能的有效手段。据玻尔兹曼电子输运理论，Seebeck系数由费米能级(EF)上下电子电导率差异决定。本项目提出通过局部改造EF附近能带结构，提升其上下非对称性，增大EF上下电子电导率差异、提升Seebeck系数的研究方案。利用稀土或过渡金属元素掺杂在PbTe中引入局域化f或d电子能级，通过调节掺杂浓度及PbTe固熔体组成调整局域化电子能级与EF之间的位置匹配，研究费米能级附近能带非对称性的演变规律、及其对PbTe化合物电输运性能的作用机制，发展能带非对称性的调控技术，明确通过能带结构非对称性改造有效提升其热电性能的材料设计方案。能带非对称性改造同时调整了电子数随能量的分布，可减弱输运电子间的能量交换，在给定电导率时降低电子热导率。基于其提升Seebeck系数同时降低电子热导率的双重贡献，本研究有望为通过能带非对称性改造提升PbTe及类似化合物热电性能提供理论和实验依据。

中文关键词： 能带工程；电子输运；热电能源转换材料

英文摘要： Band engineering has been demonstrated as an effective approach for thermoelectric performance enhancement. According to the Boltzmann theory on electron transport, Seebeck coefficient is determined by the difference on the conductivity between electrons with energy above and below the Fermi level (EF). We propose a strategy for increasing the Seebeck coefficient via a local band structure engineering to increase the up-down band asymmetry near the Fermi level and therefore for increasing the conductivity difference between electrons with energy above and below EF. This work firstly intrucduces highly localized f or d electron states into PbTe by rare-earth or transition-metal elements doping, and then adjusts the positions between these localized states and the Fermi level via a careful design of dopant concentration and matrix composition. This work focuses on the evolution of the band asymmetry near EF, the mechanism on how band asymmetry affects the electronic transport properties and the development of the technology for engineering the band asymmetry in PbTe, to clarify its optimal materials design for effectively enhancing thermoelectric performance via band asymmetry engineering. Simultaneously, band asymmetry alters the dispersion relationship between electron and energy, allowing a reduction on energy exchange between transporting electrons, and therefore, reduces the electronic thermal conductivity at a given electrical conductivity. Based on the dual effects from both increase in Seebeck coefficient and reduction in electronic thermal conductivity, this work can potentially provide theoretical and experimental basis for enhancing the thermoelectric performance in PbTe or related compounds via band asymmetry engineering.

英文关键词： Band engineering;Electronic transport;Materials for energy conversion