Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
Publication date: 4th October 2020
Colloidal nanoplatelets (NPLs) have recently emerged as a novel and exciting class of materials. While several established procedures are available for highly luminescent 4.5 monolayer and thicker NPLs, with emission spanning the green and red spectral region, typical synthesis protocols to prepare blue-emitting CdSe NPLs (λ ≈ 460 nm) yields particles with large surface areas and poor photoluminescence quantum efficiency, often accompanied by a strong emission peak from intragap trap states. Further applications may therefore be hampered by their high surface-to-volume ratio.
Here we present our work on the development of a synthesis protocol that achieves improved control over the lateral size, by exploiting a series of long-chained carboxylate precursors, varying from cadmium octanoate (C8) to cadmium stearate (C18). The length of the metallic precursor is key to tune the width and aspect ratio of the final NPLs (from 3:1 to 15:1), as well as the overall reaction yield, which increases for shorter chain length. The reduced NPL lateral dimensions lead to enhanced photoluminescence quantum efficiencies, reaching up to 30%, and good colloidal stability. As the width can be tuned down to 3.7 nm, we were able to construct also a convenient sizing curve, relating the NPL absorption position and width, and careful comparison with 4.5 monolayer NPLs demonstrate that the blue-emitting NPLs are characterized by faster emission lifetimes and a higher absorption coefficient. Via a slight adjustment, we also obtained 2.5 monolayers NPLs, with near-UV emission (λ ≈ 400 nm), and a quantum efficiency up to 11%. Our results contribute to achieving stable and efficient sources for applications such as blue and UV light emitting devices or lasers, or fast quantum light sources.
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 714876 PHOCONA).
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