Photoluminescence quantum yields for atomically thin-layered ReS2: Identification of indirect-bandgap semiconductors

Rhenium dichalcogenides have attracted considerable attention as new members of group VII layered semiconductor transition-metal dichalcogenides (TMDs) with respect to fundamental physics and potential applications. In this study, room-temperature photoluminescence (PL) spectra, as well as PL quantum yields (QYs) of thin-layer rhenium disulfide (ReS2), were evaluated. Low PL QYs of ∼10–4 were determined from a monolayer thickness to seven layers (1–7L) of ReS2 regardless of the layer number. These low PL QYs strongly suggest that the ReS2 is an indirect-bandgap semiconductor from a monolayer limit to the bulk, which is in contrast to those observed for group VI TMDs (MX2: M = Mo and W; X = S and Se). Our experimental findings will provide valuable information for the electronic and optical device applications in atomically thin-layered ReS2.