Highly bright and stable white-light-emitting cadmium-free Ag,Mn co-doped Zn–In–S/ZnS quantum dots and their electroluminescence

Abstract

Optimized white light emitting Ag,Mn:Zn–In–S quantum dots (QDs) were synthesized via a simple, scalable, reproducible, and low-cost one-pot non-injection synthetic approach. After coating a thick ZnS shell (∼12 monolayers) on the core QDs, high photoluminescence (PL) quantum yield (QY) up to 76% was achieved and high emission efficiency was retained even when the initially oil-soluble QDs were transferred into aqueous media by ligand replacement. Moreover, both thermal stability and photostability of thick shell-Ag,Mn:Zn–In–S/ZnS QDs were significantly enhanced as compared with those of Ag,Mn:Zn–In–S core QDs due to the suppressed surface defects resulting from the passivation of the dense ZnS layers. White quantum dot light-emitting diodes (QD-LEDs) were fabricated using thick shell Ag,Mn:Zn–In–S/ZnS QDs as single QDs emitter, showing good performance with maximum current efficiency of 1.86 cd A⁻¹ corresponding to external quantum efficiency (EQE) of 0.82% at a current density of 0.065 mA cm⁻², color rendering indices (CRI) of 83, Commission International d’Eclairage (CIE) coordinates of (0.344, 0.393) and correlated color temperature (CCT) of 5156 K.