Kinetics of the excitonic radiative recombination in WS2:Br2 and MoS2:Cl2 layered crystals

Due to their layered structure, 2H layered transition metal dichalcogenide indirect bandgap compounds MoS2, WS2 can be intercalated with foreign atoms and molecules. The 2H-MoS2, 2H-WS2 and 2H-WSe2 crystals intercalated with halogen molecules at low temperatures exhibit a strong luminescence due to the bound excitons recombination. In this work, the results of comparative study of the excitonic luminescence kinetics for 2H-WS2:Br2 and 2H-MoS2:Cl2 single crystals are presented. A simple kinetic model describing the temperature dependencies of the steady-state luminescence intensity and of the radiative decay time is proposed. The lifetimes of the excitonic levels and the activation energy of the excitonic luminescence quenching caused by an extrinsic self-trapping process for both studied compounds were determined.