Radiative and Non-Radiative Exciton Recombination Processes in a Chemical Vapor Deposition-Grown MoSe2 Film

In transition metal dichalcogenides (TMDs), defects and stress in thin films significantly affect the dynamic of exciton recombination. Here, we report that a MoSe2 continuous film, grown on a SiO2/Si substrate by chemical vapor deposition (CVD), shows an exceptionally strong photoluminescence (PL) and a rather long lifetime (similar to 154 ns) at 6 K. However, when the film is transferred to another similar substrate, its PL intensity is remarkably reduced by almost 80. By analyzing temperature dependent PL and time-resolved PL spectra for the as-grown and transferred films, it reveals that the strong PL of the as-grown MoSe2 sample comes from the exciton recombination from the band tails. We believe that the tensile strain introduced during CVD growth can effectively suppress the non-radiative channels of the excitons in the localized band tails. Our studies demonstrate that the effect of defects and stress on the kinetics of exciton recombination in MoSe2 is of great significance for the application of TMDs in optoelectronics.