Temperature-dependent electronic structure of γ-phase CuI: First-principles insights

To deepen the understanding of CuI that emerges as a promising next-generation transparent display material, we investigate the temperature effect on the electronic structures of its room-temperature phase γ-CuI. Using density-functional-theory-based approaches, we investigate the bandgap renormalization, which is contributed by the electron-phonon (el-ph) interaction and lattice thermal expansion. Different from most semiconductors, the bandgap widens as temperature increases, although it only widens by 88.3 meV from 0 to 600 K. In addition, based on the temperature-dependent band structure and conventional Drude model, we investigate the influences of the effective masses and evaluate the hole mobilities limited by phonon scattering along different directions. The calculated mobilities agree well with existing experimental values. Our study not only provides a fundamental understanding of the temperature effect on the electronic structure of CuI, but also gives insights for further improvement of the electronic and thermoelectric devices based on CuI.