Size-dependent third-order optical nonlinearity in colloidal CdSe/CdS core/crown nanoplatelets with quasi-type II band-structure

Colloidal semiconductor nanoplatelets, a kind of one-dimensional quantum confined materials, have been widely investigated due to their remarkable excitonic effect, in which excellent two-photon absorption property has been proved. In this work, 4.5 monolayers thick CdSe nanoplatelets laterally extended with CdS were synthesized and their crown size-dependent third-order nonlinear optical properties were measured through a picosecond Z-scan method. The detailed investigation combining the time-related photoluminescence spectroscopy reveals the effective passivation of the CdSe boundary with same area size of the core could improve the quantum yield up to 85% and third-order nonlinearity. In addition, the two-photon absorption cross-section can reach up to 6.8 x 106 GM due to the quasi-type II band structure of these core/crown nanoplatelets.

Automated summary

In this study, 4.5 monolayers thick CdSe nanoplatelets extended with CdS were synthesized, and their third-order nonlinear optical properties were measured. The effective passivation of CdSe boundary improved the quantum yield and third-order nonlinearity. These core/crown nanoplatelets exhibited excellent two-photon absorption property due to their quasi-type II band structure.