Phonon-Mediated Ultrafast Hole Transfer from Photoexcited CdSe Quantum Dots to Black Dye

We have applied non-adiabatic molecular dynamics (NAMD) and the Fewest Switching Surface Hopping (FSSH) method to simulate the energy dissipation and charge transfer processes in a CdSe quantum dot (QD) functionalized by the tris-thiocyanato-ruthenium (II) terpyridine complex, referred to as black dye. Our calculations reveal ultrafast hole transfer from the photoexcited QD to the dye, despite a significant energy splitting between QD's and dye's occupied states. The mechanism of such ultrafast QD-to-dye hole transfer is rationalized by strong non-adiabatic couplings between the delocalized surface orbitals of the QD and the high-frequency vibrations of isothiocyanate ligands of the black dye. This mechanism is also confirmed by a very rapid loss of coherency of the excitation due to strong electronic couplings with vibrational modes of the dye. © 2019 American Chemical Society. All rights reserved.