Effect of PMMA polymer matrix on optical properties of CdSe nanoplatelets

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 optoelectronic properties of cadmium chalcogenide NPLs. We demonstrate that incorporation of CdSe NPLs into a poly(methyl methacrylate) (PMMA) matrix leads to a red-shift in 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.

Automated summary

A new method to tune the optoelectronic properties of cadmium chalcogenide nanoplatelets (NPLs) by incorporating CdSe NPLs into a PMMA matrix is reported in this study. The red-shift in excitonic transitions and band-edge emission of NPLs induced by the polymer matrix depends on the thickness of the NPLs. This simple approach allows for adjusting the optical and electronic properties of NPLs without altering their sizes and composition, showing potential for various practical applications.