Quantum Confinement-Tunable Ultrafast Charge Transfer in a PbS Quantum Dots/WSe 0D-2D Hybrid Structure: Transition from the Weak to Strong Coupling Regime.

0D-2D mixed-dimensional hybrid structures, which combine tunable optical properties of 0D quantum dots (QDs) and high transport mobilities of 2D layered materials, have shown great potential in optoelectronic applications. Understanding charge transfer dynamics at the 0D-2D interface is essential but still lacking. Here, using PbS QD/WSe system, by simply controlling PbS QD size, we show a tunable hole transfer (HT) rate by more than 4 orders of magnitude (from ∼1 ns to <100 fs) and, interestingly, transition from the weak to strong coupling regime due to quantum confinement effect. In contrast to reported layer-dependent energy transfer dynamics, we observe a robust HT rate against WSe layer number, which can be ascribed to a subtle change of WSe valence band structure with layer number. Our results are important to not only fundamental understanding of charge transfer behavior at nanoscale low-dimensional interface but also help design next-generation mixed-dimensional optoelectronic devices.