High responsivity in ReS₂-based optoelectronic devices: A first-principles study

Rhenium disulfide (ReS₂), a member of the group-VII transition metal dichalcogenides (TMDs) family, has attracted attention for applications of optoelectronic devices with its exotic properties, such as the optical anisotropy and weak interlayer coupling. Experimental studies reported that ReS₂-based phototransistors exhibit high responsivity, which is a crucial requirement for photodetector devices, but its origin has not been systematically studied yet. In this presentation, based on the combined density functional theory (DFT) calculation and the delta self-consistent field (ΔSCF) method, we investigate optical excitation behaviors of possible single-atom vacancies in monolayer ReS₂. Since the classical ΔSCF scheme has limited applicability within the localized systems, we newly establish extended formalism to be utilized in general solid systems. Using the developed ΔSCF method, we present optical excitation process in the monolayer ReS₂ and observe the formation of trapped electrons below conduction band. Our study provides theoretical background for applications of ReS₂-based optoelectronic devices as well as the new methodology within the DFT for treating the optical excitation in general systems.