Controlling Quantum‐Confined Stark Effect in Coupled II–VI Quantum Dots by Interface Engineering

Electric-field tuning of excitonic states in confined systems via the quantum-confined Stark effect (QCSE) provides a flexible way for electro-optic modulation with great efficiency. In epitaxial and colloidal quantum dots (QDs), the interdot coupling allows additional degrees of freedom for optical switches. Here QCSE is explored in artificial molecules formed by two coupled QDs of main group II-VI elements. Compared with a single QD, the QCSE is remarkably enhanced in QD molecules and highly tunable by the interdot coupling strength as well as by homo- and hetero-dimerization of QDs. In addition, the strong coupling between QDs can retard charge separation under an external electric field and even bring the electron and hole states from two QDs into a resonance, thereby boosting the fluorescence emission in QD molecules. These mechanistic understandings provide vital guidelines for fine manipulation of electron, spin, and exciton in coupled QDs and their assemblies for tunable optoelectronics, photonics, and quantum information applications.