Coupling in Quantum Dot Molecular Hetero-Assemblies

TL;DR

This study investigates how the interaction mechanisms between small hetero-assemblies of CdSe quantum dots vary with interparticle distance, providing insights into charge and energy transfer processes relevant for optoelectronic device optimization.

Contribution

It introduces a method to systematically tune and analyze the coupling mechanisms in quantum dot hetero-assemblies based on interparticle distance and surface crystallography.

Findings

Coupling mechanisms range from charge transfer to energy transfer depending on distance.

Nearest surfaces involved in linkage are the (101) faces.

Spectroscopic analysis rationalizes the interaction mechanisms.

Abstract

The design of large-scale colloidal quantum dots (QDs) assemblies and the investigation of their interaction with their close environment are of great interest for improving QD-based optoelectronic devices' performances. Understanding the interaction mechanisms taking place when only a few QDs are assembled at a short interparticle distance is relevant to better promote the charge or energy transfer processes. Here, small hetero-assemblies formed of a few CdSe QDs of two different sizes, connected by alkyl dithiols, are fabricated in solution. The interparticle distance is tuned by varying the linear alkyl chain length of the bifunctional spacer from nanometer to sub-nanometer range. The crystallographic analysis highlights that the nearest surfaces involved in the linkage between the QDs are the (101) faces. The thorough spectroscopic investigation enables a sound rationalization of the coupling mechanism between the interacting nanoparticles, ranging from charge transfer/wavefunction delocalization to energy transfer, depending on their separation distance.