Rationally designed synthesis of bright Cu–Ga–Zn–Se-based nanocrystals for efficient green quantum-dot light-emitting diodes

Abstract

I–III–VI-group semiconductor nanocrystals (NCs) have received extensive attention for use in quantum-dot light-emitting diodes (QLEDs) due to their nontoxic nature, large-scale tunable emission wavelength and straightforward synthesis. At present, research on ternary CuGaSe₂ (CGSe) NCs is gradually being carried out. CGSe-based semiconductor NCs with a wide and tunable bandgap exhibit significant promise for efficient QLEDs preparation. In order to improve their functionality, stability and dispersion, Zn²⁺ was introduced into CGSe cores, which were coated with wide-band-gap ZnS to form Cu–Ga–Zn–Se/ZnS NCs to improve their luminescence performance. In this work, a series of Cu–Ga–Zn–Se/ZnS NCs with tunable emission from 603 to 524 nm and a photoluminescence quantum yield (PLQY) of 96% could be acquired by precisely controlling the non-stoichiometric Cu : Ga molar ratios in the synthesis of the CGZSe cores. Furthermore, green luminescent CGZSe/ZnS NCs were obtained by adjusting the amount of crucial Zn precursors during nucleation and shell formation. The green QLEDs based on these NCs show a high external quantum efficiency of 5.8% and a high brightness of 7016 cd m⁻². This work reveals new possibilities for the design of novel and efficient Cd-free green QLEDs.