Charge Transfer Dynamics of Core–Shell Quantum Dots and MoS₂ Nanocomposites Using Transient Absorption Spectroscopy

Photoluminescence (PL) quenching mechanisms and charge transfer dynamics of CdTe/CdS quantum dots (QDs) and molybdenum disulfide (MoS2) nanocomposites were explored by using steady-state and transient absorption spectra. The PL intensity of QDs can be quenched by up to 97% at 0.35 mg/mL MoS2. In the presence of MoS2, the ground state bleaching feature of MoS2 appeared in the transient absorption spectrum of CdTe/CdS–MoS2 nanocomposites. This is attributed to the electrons of QDs being injected into the band edge of MoS2. With increasing MoS2, there was a red-shifted ground state bleaching, indicating that more band edge electrons lead to a redistribution of the electric field of MoS2, and the energy level of MoS2 is decreased. The larger space charge separation of electrons and holes in the nanocomposites would slow down charge recombination, bringing about a slower stimulated emission feature. By adjusting the MoS2 concentration, we can modulate the charge-transfer dynamics, which may open up new opportunities for the design of optoelectronic devices.