Optical and thermoelectric properties of non-Janus CuI and AgI, and Janus Cu2BrI and Ag2BrI monolayers by many-body perturbation theory

In an outstanding experimental advance in the field of two-dimensional nanomaterials, cuprous iodide (CuI) and silver iodide (AgI) monolayers have been grown via a novel graphene encapsulation synthesis approach [Adv.Mater.2022, 34, 2106922]. Inspired by this accomplishment, we conduct first-principles calculations to investigate the elastic, phononic thermal transport, electronic, and optical properties of the native CuI and AgI and Janus Cu2BrI and Ag2BrI monolayers. Electronic and excitonic optical properties are elaborately studied using the many-body perturbation theory on the basis of GW approximation. Our results indicate that these novel systems are stable but with soft elastic modulus and ultralow lattice thermal conductivity. It is also shown that the studied monolayers are wide-gap semiconductors with exciton binding energies close to 1 eV. The effects of mechanical straining and electric field on the resulting electronic and optical properties are also analyzed. The presented first-principles results provide a deep understanding of the stability, phononic transport, and tunable optoelectronic properties of the native CuI and AgI and Janus Cu2BrI and Ag2BrI monolayers, which can serve as a guide for the oncoming studies.