Ultrafast Charge Transfer Enhancement in CdS-MoS2 via Linker Molecule

TL;DR

This study uses TD-DFT to show that ligand molecules significantly enhance ultrafast charge transfer in CdS-MoS2 heterostructures, with transfer dynamics influenced by temperature and excitation density.

Contribution

It reveals the role of linker molecules in boosting charge transfer speed in CdS-MoS2 systems, a previously poorly understood aspect.

Findings

Ligand molecules enhance ultrafast charge transfer.

Electrons transfer from CdS to MoS2 as band alignment predicts.

Charge transfer dynamics depend on temperature and excitation density.

Abstract

Hybrid systems, which take advantage of low material dimensionality, have great potential for designing nanoscale devices. Quantum dots (QDs) -- a 0D nanostructure -- can be combined with 2D monolayers to achieve success in photovoltaics and photocatalytic water splitting. In such colloidal systems, ligand molecules such as cysteine play an important role in device performance. The role of the ligand molecule in these QD heterostructures is poorly understood. In this study, time-dependent density functional theory (TD-DFT) is employed in order to explore how the ligand affect the charge transfer at the ultra-fast timescale. We study the charge transfer dynamics in CdS-MoS2 heterostructures both with and without an organic linker molecule. We find that the ligand molecule enhances the ultrafast charge transfer, and that electrons are preferentially transferred from CdS to MoS2 as band alignment would predict. The electronic dynamics and time-evolved projection character are sensitive to the ionic temperature and excitation density.