(199j) Revealing the Enigmatic Interfacial Layer of Core/Shell Quantum Dots

Colloidal quantum dots (QDs) are attractive materials for lasers, displays and other light-emitting applications due to their narrow spectral emission bandwidth, size-tunable bandgap and high-photoluminescence quantum yield (PLQY). However, QDs undergo inevitable degradation of their unique optical properties over time due to their sensitive surface chemistry. To overcome these limitations, several approaches have been used, such as overcoating with an inorganic semiconductor shell of a wider band gap (core/shell hetrostructures), surface functionalization with organic and inorganic ligands, or polymer coating and composite formation. In particular, core/shell heterostructured QDs with thick shells [so called “giant” QDs (g-QDs)] have shown dramatically modified single-dot properties (non-blinking, non-photobleaching) and clear suppression of non-radiative recombination pathways (Auger recombination, photoexcited-carrier surface trapping). However, we have recently determined that the outstanding properties afforded by the g-QD’s thick shell are sensitive to both the shell-structure quality (crystal defects) and the properties of the interfacial layer (sharp or smooth core/shell interface). In particular, the useful “lifetime” of the g-QD under conditions of elevated temperature and exposed to air or water is strongly dependent on these structural and interface properties. Significantly, we have further revealed that these aspects of the internal nanoscale structure can be precisely tailored by choice of synthetic parameters. Here, we will present our recent results on understanding this critical synthesis-structure-function nexus.