Application of angle-resolved photoemission spectroscopy in thermoelectric materials research

Thermoelectric materials, which enable the direct conversion of thermal energy into electrical energy, play a significant role in thermoelectric power generation and cooling technologies. The electrical transport properties of thermoelectric materials are determined by their band structure, and angle-resolved photoemission spectroscopy (ARPES) is the most intuitive technique for probing band structures. To date, while numerous review articles have separately discussed ARPES technology and thermoelectric materials, there is an absence of review focusing on the application of ARPES technology in thermoelectric materials research. This review begins with a brief introduction to the basic parameters of thermoelectric materials and the impact of their band structure on transport properties. It then introduces the basic principles and sample preparation requirements of ARPES technology. Following this, detailed discussions of several typical applications of ARPES technology in the study of thermoelectric materials are presented. Finally, the review provides a summary and outlook. This review comprehensively explores the application of angle-resolved photoemission spectroscopy (ARPES) technology in the study of thermoelectric materials, highlighting the importance of this technique for understanding the relationship between material band structure and thermoelectric performance. Utilizing ARPES technology allows for precise measurements of the Fermi level position, the shape of individual bands, and the evolution trends of multiple bands, which are crucial for optimizing the performance of thermoelectric materials. The review also discusses the effects of temperature, doping, and defects on the band structure, offering a new perspective for the regulation of thermoelectric performance. Additionally, the review introduces the potential impact of band folding, van Hove singularities, and two-dimensional electron gases on thermoelectric performance. Since the discovery of the Seebeck effect, the study of thermoelectric materials has spanned two centuries. In addition to experimental efforts, theoretical understanding of the fundamental transport mechanisms has been the key to advancing the research field. Future research on thermoelectric materials should place greater emphasis on uncovering microscopic mechanisms. Given the indispensable role of ARPES in probing the band structure of solids, it is foreseeable that the application of ARPES technology in thermoelectric materials will become increasingly widespread. With the interdisciplinary development of the field, it is anticipated that materials or mechanisms with higher thermoelectric performance will be discovered within the traditional subjects of ARPES research. In the future, breakthroughs in thermoelectric performance may be achieved by, for instance, experimentally exploring the thermoelectric properties of strongly correlated materials, investigating the coupling and application of low-dimensional thermoelectric materials in micro- and nano-devices, and employing various modulation methods such as magnetic fields, light, and strain.