Synthesis and Fluorescence Upconversion Properties of CdSe/CdS/CdTe Hetero-structured 2D Colloidal Nanocrystals
Ali Khan a, Guillaume Bertrand b, Ayelet Teitelboim c, Chandra Sekhar Mutyala a, Anatolii Polovitsyn b, Rosaria Brescia b, Josep Planelles d, Juan Climente d, Dan Oron c, Iwan Moreels a
a Gent University - BE, Krijgslaan 281 - S3, Gent, Belgium
b Istituto Italiano di Tecnologia (IIT), Genova, Via Morego, 30, Genova, Italy
c Department of Physics of Complex Systems, Weizmann Institute of Science, Herzl Street, 234, Rehovot, Israel
d Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, Spain
Poster, Ali Khan, 010
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.

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