Thermoelectric materials (TMs) can uniquely convert waste heat into electricity, which provides a potential solution for the global energy crisis that is increasingly severe. Bulk Cu₂Se, with ionic conductivity of Cu ions, exhibits a significant enhancement of its thermoelectric figure of merit zT by a factor of ~3 near its structural transition around 400 K. Here, we show a systematic study of the electronic structure of Cu₂Se and its temperature evolution using high-resolution angle-resolved photoemission spectroscopy. Upon heating across the structural transition, the electronic states near the corner of the Brillouin zone gradually disappear, while the bands near the centre of Brillouin zone shift abruptly towards high binding energies and develop an energy gap. Interestingly, the observed band reconstruction well reproduces the temperature evolution of the Seebeck coefficient of Cu₂Se, providing an electronic origin for the drastic enhancement of the thermoelectric performance near 400 K. The current results not only bridge among structural phase transition, electronic structures and thermoelectric properties in a condensed matter system, but also provide valuable insights into the search and design of new generation of thermoelectric materials.

热电材料（TMs）可以独特地将废热转化为电能，这为日益严重的全球能源危机提供了潜在的解决方案。块状 Cu ₂ Se 具有 Cu 离子的离子电导率，在 400 K 左右的结构转变附近，其热电品质因数zT显着提高了约 3 倍。在这里，我们对 Cu 的电子结构进行了系统研究_2个使用高分辨率角分辨光电子能谱分析硒及其温度演变。在结构转变过程中加热时，布里渊区角附近的电子态逐渐​​消失，而布里渊区中心附近的能带突然转向高结合能并形成能隙。_{有趣的是，观察到的带重建很好地再现了 Cu 2}的塞贝克系数的温度演变Se，为 400 K 附近热电性能的显着增强提供了电子来源。目前的结果不仅在凝聚态物质系统中的结构相变、电子结构和热电性质之间架起桥梁，而且为搜索和设计提供了有价值的见解新一代热电材料。