Effect of PMMA polymer matrix on optical properties of CdSe nanoplatelets

Abstract

Abstract Colloidal cadmium chalcogenide nanoplatelets (NPLs) possess unique properties such as ultrapure emission and giant-oscillator strength originating from their atomically-flat surfaces and one-dimensional carrier confinement. However, unlike quantum dots, the NPLs do not provide continuously tunable absorption and emission, which restricts the range of their possible applications. In this paper, we report a new approach for tuning opto-electronic properties of cadmium chalcogenide NPLs. We demonstrate that incorporation of CdSe NPLs into a poly(methyl methacrylate) (PMMA) matrix leads to red-shifting of all the low energy excitonic transitions and band-edge emission of the NPLs. The polymer matrix induced red-shift of the band-edge emission depends on thickness of the NPLs and ranges from 109 to 253 meV for 4.5 and 2.5 monolayer thick CdSe NPLs, respectively. In the case of CdSe/CdS core-shell NPLs, the polymer matrix induced red-shift of emission peak strongly depends on thickness of the shell and becomes negligible for thick shell CdSe/CdS core-shell NPLs. Possible explanations for the observed effect are presented. The demonstrated here simple approach allows one to tune optical and electronic properties of cadmium chalcogenide NPLs without altering their sizes and composition, which makes it interesting for different practical applications.