InP/ZnSeS/ZnS Quantum Dots with High Quantum Yield and Color Purity for Display Devices

To achieve the quantum yield and color purity suitable for applications to the visible emitters in display devices, the optical features of indium phosphide (InP) quantum dots (QDs) are improved. Two types of InP cores are synthesized with two kinds of the phosphorus precursors, tris(trimethylsilyl)phosphine and tris(dimethylamino)phosphine. The prepared cores are fabricated for the gradient-alloyed inner shell (ZnSeS) and outer shell (ZnS) to complete the environmentally benign QDs with the structures of core/inner-shell/outer-shell. The quantum yields in the two types of QDs are 95 and 85% with the bandwidths of 35 and 36 nm, respectively, comparable to the characteristics of state-of-the-art InP QDs. The band-to-band transition of the neutral states in QDs turns out to be more efficient than the band-to-hole transition, whereas the optical transitions of the charged states are not strong. Despite the similar peak shapes with the equivalent Stokes shift, the optical features investigated by temperature-dependent and time-resolved spectroscopy are distinctive in the two types of QDs. In particular, the formation of the charged states and localized states, in addition to the dark states, is influenced by the precursors. These findings suggest strategies to enhance the quantum yield and color purity of InP QDs for applications to display devices with a green chemistry approach.