Journal of Physical Chemistry B, Vol.102, No.20, 3906-3911, 1998
Trap state dynamics in MoS2 nanoclusters
The trap-to-trap relaxation and recombination dynamics of photogenerated electron/hole pairs in MoS2 nanoclusters have been studied. Static and time-resolved emission experiments have been performed on 3.0 and 4.5 nm diameter nanoclusters in ternary inverse micelles, acetonitrile, and octane at room temperature and at 20 K. The results indicate that, following synthesis in ternary inverse micelles, the nanoclusters have both shallow and deep traps. The deep traps are retained upon extraction into acetonitrile and passivated upon charge neutralization and reextraction into octane. The emission kinetics show that trap-to-trap relaxation is fast (<40 ps) at room temperature and slows (similar to 200 ps) at 20 K. A distributed kinetics model is presented that quantitatively describes electron/hole recombination. The trapped electron Bohr radius is found to be 2.0-2.5 nm in all cases. Charge neutralization and reextraction into octane passivates both the deep and the shallow traps on some nanoclusters, resulting in indirect band edge emission at 20 K.
Keywords:ELECTRONIC-STRUCTURE;COLLOIDAL SEMICONDUCTORS;CDS PARTICLES;CLUSTERS;PHOTOCHEMISTRY;SPECTROSCOPY;WSE2