Quantum Confined Stark Effect in Phase-Pure Thick-Shell CdSe/CdS Quantum Dots*

Colloidal semiconductor quantum dots (QDs) have recently attracted great attention in electric fields sensing via the quantum confined Stark effect (QCSE), Here, the QCSE in ensemble of phase-pure wurtzite CdSe/CdS QDs is studied by applying a uniform external electric field. We observe a clear field-dependent PL and absorption modulations, including the spectral shifts and broadening, as well as the changes in its intensity. The Stark shifts in ensemble emission and absorption are found to be typical quadratic function of the external field. Moreover, the multiexciton states also exhibit obvious optical responses to the electric field, with a decrease of 18% in emission intensities and an increase in the ultrafast lifetime from 25 to 31 ps. The results imply that the field-induced QCSE in the QD ensemble are attributed to the effective suppression of the primary source of local field in such thick-shell QDs, thus proving that an efficient field control over the optical properties (the changes in emission and absorption intensity, spectral shifts, and PL lifetime) in these nanoparticles is feasible and open the potential possibility of field-sensitive QDs to achieve real-time electro-optic sensing.