Efficient Photoexcited Charge Separation at the Interface of a Novel 0D/2D Heterojunction: A Time-Dependent Ultrafast Dynamic Study

To achieve efficient conversion and avoid loss of solar energy, ultrafast charge separation and slow electron-hole recombination are desired. Combining time-dependent density functional theory (TD-DFT) with nonadiabatic molecular dynamics, Au-9(PH3)(8)/MoS2, as a prototype for zero-dimensional/two-dimensional (0D/2D) heterojunction, has been demonstrated to present excellent light absorption capacity and effective charge separation characteristics. In the heterojunction, photoexcitation of the Au-9(PH3)(8) nanocluster drives an ultrafast electron transfer from Au-9(PH3)(8) to MoS2 within 20 fs, whereas photoexcitation of the MoS2 nanosheet leads to hole transfer from MoS2 to Au-9(PH3)(8) within 680 fs. The strong nonadiabatic coupling and prominent density overlap are responsible for the faster electron separation relative to hole separation. In competition with the charge separation, electron-hole recombination requires 205 ns, ensuring an effective carrier separation. Our atomistic TD-DFT simulation provides valuable insights into the photocarrier dynamics at the Au-9(PH3)(8)/MoS2 interface, which would stimulate the exploration of 0D/2D hybrid materials for photovoltaic and optoelectronic devices.