Abstract:

The charge redistribution upon optical excitation of various necked homodimer colloidal quantum dot molecules (CQDMs) is investigated using single-particle emission spectroscopy. By tuning the hybridization of the electron wavefunctions at a fixed center-to-center distance through controlling the neck girth, we reveal two coupling limits: on one hand, a ‘‘connected-but-confined’’ situation where neighboring CQDs are weakly fused to each other, manifesting a weak-coupling regime, and on the other hand, a ‘‘connected-anddelocalized’’ situation where the neck is filled beyond the facet size, leading to a rod-like architecture manifesting strong coupling. The interplay between the radiative and non-radiative Auger decays of these states turns emitted photons from the CQDMs in the weakcoupling regime highly bunched unlike CQD monomers, while the antibunching is regained at the strong-coupling regime. This work sets an analogy for the artificial molecule CQDMs with regular molecules, where the two distinct regimes of weak and strong coupling correspond to ionic- or covalent-type bonding, respectively.