Proceedings of Online Meetup: Shape-Controlled Nanocrystals: Synthesis, Characterization Methods and Applications (ShapeNC)
Publication date: 6th May 2020
Colloidal semiconductor nanoplatelets heterostructures are interesting as they combine strong confinement of excitons in 2D materials with a wide range of possible semiconductor junctions due to a template-free, solution-based growth. Here we demonstrate a ternary 2D architecture consisting of a core of CdSe, laterally encapsulated by a type-I barrier of CdS, and finally a type-II outer layer of CdTe as so-called crown. The CdS acts as a tunneling barrier between CdSe- and CdTe-localized hole states, and through strain at the CdS/CdTe interface, it can induce a shallow electron barrier for CdTe-localized electrons as well. Consequently, next to an extended fluorescence lifetime, the barrier also yields emission from CdSe and CdTe direct transitions. This unique configuration further enables two-photon as well as three-photon fluorescence upconversion.