ULTRAFAST CHARGE-TRANSFER DYNAMICS AT SNS2 SURFACES

The carrier dynamics at dye-sensitized SnS2 surfaces were studied using a variety of picosecond techniques. Fluorescence quenching studies of the rate of electron injection from adsorbed oxazine into the conduction band have determined the rate to be 3 x 10(13) s-1, corresponding to an electron-transfer time of 40 +/- 20 fs. The corresponding localization of the free carrier in the conduction band of the semiconductor is observed to occur in 1-10 ps. Picosecond pump-probe studies of the ground-state recovery of the oxazine determine the back-electron-transfer process to occur on the 10-ps time scale. Theoretical justification for the initial electron injection time scale is offered using the complete molecular Liouville equation within the Mori-Zwanzig projection operator formalism.