Relaxation and electron transfer dynamics in bare and DTDCI sensitized MoS2 nanoclusters

The trapping dynamics of photogenerated electrons and holes in MoS2 nanoclu sters has been studied using time resolved emission polarization and absorp tion spectroscopies. These results are compared to absorption kinetics obta ined on MoS2 nanoclusters with adsorbed DTDCI (DTDCI=diethylthiodicarbocyan ine iodide) dye. The results indicate that emission from the MoS2 band edge state is polarized, while emission from trapped electrons and holes is unp olarized. This polarization difference is used to obtain the electron and h ole trapping times and values of 275 ps and 42 ps, respectively, are obtain ed. Decays having the same time constants are observed in the transient abs orption results. The results obtained on the MoS2/DTDCI system show that el ectron injection occurs with a time constant of 12 ps. These kinetics also show a 225 ps decay component which is assigned to electron trapping and re verse electron transfer. The 225 ps decay time along with the 275 ps trappi ng time indicates that reverse electron transfer from the conduction band h as a time constant of about 1.2 ns. Following trapping, reverse electron tr ansfer from deep traps is slow. (C) 2000 American Institute of Physics. [S0 021- 9606(00)70337-0].