Colloidal nanoplatelets (NPLs) have recently emerged as a novel and exciting class of materials. Several established procedures are available for highly luminescent NPLs, with emission spanning the green and red spectral regions[1,2]. However, typical synthesis protocols to prepare blue-emitting CdSe NPLs (λ ≈ 460 nm) yields NPLs with large surface areas and poor photoluminescence quantum efficiency, often accompanied by a strong emission peak from intragap trap states[3]. Device applications may therefore be hampered. We present the development of a synthesis protocol that achieves improved control over NPLs 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 green-emitting NPLs demonstrate that the blue-emitting NPLs are characterized by faster emission lifetimes and a higher absorption coefficient.

Bright blue CdSe nanoplatelets: Synthesis and size control

ACS Spring Meeting 2021

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