Color-tunable optical properties of cadmium-free transition metal ions doped InP/ZnS quantum dots

Cadmium-free InP quantum dots (QDs) exhibit many unique optical properties, and show great promise as light emitting materials. In this work, a series of high-efficient and color-tunable transition metal ions (Cu, Mn) single- and co-doped InP/ZnS QDs with the average size of 3.2-3.7 nm, were firstly prepared via a nucleation-doping method in an organic synthetic route. These three kinds of doped InP/ZnS QDs all exhibit dual emission with one peak position around green region owing to the intrinsic state and the other peak position around orange-red region resulted from dopant emission, the relative intensity of which can be effectively tuned by varying Cu or Mn dopant concentration. The dopant emission of Cu doped InP/ZnS QDs from 572 to 696 nm can be realized via increasing Cu dopant concertration from 0.25% to 10%, while the peak position of dopant emission in Mn doped InP/ZnS QDs system remains unaltered as Mn dopant concentration increasing. Besides, the interaction mechanism of Cu and Mn dopant in co-doped InP/ZnS QDs system was investigated with steady-state and time-resolved PL spectroscopy measurements. The results reveal that the dopant emission is dominated by Cu doping rather than Mn doping. These unique results in doped InP/ZnS QDs would help to understand the fundamental aspects of doping, and the dual-emissive and color-tunable optical properties of single-phase doped InP/ZnS QDs will endow them with great promise as color-converting materials for use in solid-state lighting.