Temperature Effects on the Electronic Structure of Thermoelectric SnSe from First-Principles

Tin selenide (SnSe) has attracted intense interest as a high-performance thermoelectric material, yet the temperature evolution of its electronic band structure remains insufficiently understood. Here, we present comprehensive first-principles calculations on the temperature-dependent electronic structure of SnSe. Using hybrid-functional electronic structure calculations combined with state-of-the-art electron–phonon self-energy method, we systematically separate the contributions from lattice thermal expansion and phonon-induced band renormalization. Our calculations show that thermal expansion and phonon-induced renormalization produce distinct effects on the band structure, and only their combined treatment reproduces experimental trends and the band gap values. Phonon-induced renormalization dominates the overall gap reduction and exhibits pronounced valley-dependent behavior, substantially modifying the electronic landscape relevant for carrier transport. These results provide quantitative insight into the temperature evolution of the electronic structure governing thermoelectric performance in SnSe and establish the necessity of explicitly including electron–phonon coupling for accurate prediction of high-temperature electronic and transport properties.