White-light-emitting Cu,Mn co-doped Zn–In–S/ZnS quantum dots with high stability and their electroluminescence

Abstract

We developed a facile noninjection synthetic method to prepare white light-emitting Cd-free thick shell Cu,Mn:Zn–In–S/ZnS quantum dots (QDs) with high stability. Based on systematic research on the relationship between shell thickness and QD stability, it was demonstrated that overcoating thick ZnS passivation layers (∼7.9 monolayers) onto a Cu,Mn:Zn–In–S core could improve the photoluminescence quantum yield (PL QY) substantially up to 75% and the high PL QY could be maintained after the initial oil-soluble QDs were transferred into aqueous media via ligand exchange. The PL lifetime of thick shell Cu,Mn:Zn–In–S/ZnS QDs increased remarkably by 30-fold (from 0.13 μs to 3.50 μs). Also, the prominent thermally and photochemically stable properties of the resultant thick shell QDs have been ascertained. Moreover, gram-scale white emission Cu,Mn:Zn–In–S/ZnS QDs could be prepared in a single batch reaction via the noninjection synthetic approach. In addition, the as-obtained white emissive Cu,Mn:Zn–In–S/ZnS QDs could be employed in white quantum dot light-emitting diode (QD-LED) devices and have shown good performance with a lower turn-on voltage of 5.7 V and color rendering indexes (CRI) as high as 85, indicating that Cu,Mn:Zn–In–S/ZnS QDs could be a potential candidate in QD-based lighting or solid-state lighting as a single color-converting material.