Efficient Near-Infrared CdSe/CdZnSe/CdZnS Core/Shell/Shell Nanoplatelet Light-Emitting Diodes by Controlling Gradient Alloy Shells

Colloidal nanoplatelets (NPLs) have attracted significant attention for light-emitting diodes (LEDs) owing to their strong in-plane dipole moments and intrinsically narrow emission linewidth. In this study, we report the synthesis of near-infrared (NIR)-emitting CdSe/CdZnSe/CdZnS core/shell/shell NPLs with uniform size and well-controlled shell composition. The optimized NPLs exhibit a PL emission peak at 715 nm, a narrow full width at half maximum of 21 nm, and a high photoluminescence quantum yield of 54%. The gradient-alloy CdZnSe/CdZnS shell effectively suppresses nonradiative recombination and enhances carrier confinement within the CdSe core. Consequently, solution-processed LEDs incorporating these NPLs achieve a low turn-on voltage of 1.8 V and a maximum luminance of 6415 cd m^–2. This work establishes an effective synthetic strategy for gradient-shell CdSe NPLs and provides a promising platform for high-performance NIR optoelectronic devices.