Article Cite This: J. Phys. Chem. C XXXX, XXX, XXX−XXX
pubs.acs.org/JPCC
Long-Lived Emission in Type-II CdS/ZnSe Core/Crown Nanoplatelet Heterostructures Sushma Yadav, Ajeet Singh, and Sameer Sapra* Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India ABSTRACT: The synthesis of core/crown heterostructures allows us to modify the properties of nanoplatelets (NPLs) by altering the lateral dimensions without affecting their thickness, that is, the confinement direction. We have presented the synthesis and study of photophysical properties of type-II CdS/ ZnSe core/crown NPLs, where electron-wave function is confined to CdS core, while hole wave function resides in ZnSe crown. The recombination of the photogenerated excitons in CdS and ZnSe occurs across the interface of both semiconductors and due to which the emission shows a red shift of ∼100 nm. The lifetime of CdS/ZnSe increases almost two orders of magnitude in comparison with the core CdS NPLs. The fast decaying excited states of the NPLs are distributed over the CdS/ZnSe interface and slow down; the larger lifetimes allow for their potential utilization in applications requiring charge separation.
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INTRODUCTION The semiconductor nanocrystals (NCs) exhibiting quantum confinement display very interesting optoelectronic properties due to which they have been used in various applications such as photovoltaics, photocatalysis, light-emitting diodes, bioimaging, and so on.1−7 The properties of the NCs can be tuned, improved, as well as modified by varying size, shape, and surface composition.8 Until now, semiconductor NCs of various shapes such as spherical quantum dots,9 nanorods,10 tetrapods,11 nanowires,12 and nanoribbons13 have been synthesized and studied extensively. Recently, 2D nanoplatelets (NPLs) of CdE (E = S, Se, and Te) have been successfully synthesized with precisely controlled thickness on the atomic scale.14−16 The NPLs exhibit 1D quantum confinement, due to which they display exciting optoelectronic properties. These NPLs display very sharp absorption and emission features that are tunable as a function of thickness. Moreover the photoluminescence (PL) shows a very small Stokes shift (1− 3 nm) w.r.t. the absorption peak. This extremely narrow emission bandwidth (
