Narrow electroluminescence in bromide ligand-capped cadmium chalcogenide nanoplatelets
Colloidal zinc blende II–VI semiconductor nanoplatelets (NPLs) demonstrate as a promising class of materials for optoelectronic devices due to their unique excitonic characteristics, narrow emission linewidth, and quantum well-structure. Adopting heterostructures for these nanocrystals allows tuning of their optical features and enhances their photostability, photoluminescence (PL), quantum yield (QY), and color purity for further device integration. Exchanging of carboxylate capping ligands on top and bottom  facets of CdSe NPLs with halide ligands is an alternative to achieve the aims of spectral tunability and improve surface passivation, but to date there have been no reports on integrating the advantages of halide ligand exchanged CdSe NPLs for device fabrication. In this work, we demonstrate green electroluminescence (EL) of bromide ligand-capped CdSe NPLs as active emitters in an electrically driven light emitting diode (LED) with a low turn-on voltage of 3.0 V. We observed EL emission at 533.1 nm with a narrow linewidth of 19.4 nm, a maximum luminance of 1276 cd/m2, and the highest external quantum efficiency (EQE) of 0.803%. These results highlight the ability of halide ligand exchange in tuning the EL properties of CdSe NPL-LEDs and potential of bromide ligand-capped CdSe NPLs in contributing to the green emission region of NPL-LEDs, demonstrating its potential for future device integration and contribution to a high color rendering index of future NPL displays.