Two-dimensional group-VI transition metal dichalcogenide semiconductors, such as MoS2,
WSe2, and others, exhibit strong light-matter coupling and possess direct band gaps in the
infrared and visible spectral regimes, making them potentially interesting candidates for
various applications in optics and optoelectronics. Here, we review their optical and
optoelectronic properties with emphasis on exciton physics and devices. As excitons are
tightly bound in these materials and dominate the optical response even at room …