Ultrafast Electron Transfer Dynamics Affected by Ligand Chain Length in InP/ZnS Core/Shell Quantum Dots

Efficient charge transfer is closely related to improvement of the performance of quantum dot (QD)-based solar cells. In this paper, the effects of surface ligands with different alkyl chain lengths ((1-dodecanethiol (DDT) and 1-octanethiol (OT)) on the electron transfer process in InP/ZnS QDs were studied by ultrafast spectroscopy. With adsorption of the electron acceptor anthraquinone (AQ), both hot electron transfer and band-edge electron transfer between the QDs and acceptor were observed. The analysis shows that there is a more efficient (hot) electron transfer process in shorter-chain ligand OT-capped QDs compared with DDT-capped QDs, which is probably because of the improved passivation and lower density of trap states for OT-capped QDs in which electron trapping may compete with electron transfer and reduce the efficiency of electron transfer. This work enhances the understanding of how the chain length of ligands affects the electron transfer process from the perspective of ultrafast photophysical properties, and it may provide valuable insight into how to improve the performance of optoelectronic devices through surface-ligand engineering.