Synthesis and optical properties of tunable dual emission copper doped CdTe1-xSex alloy nanocrystals

Tunable and dual emission Cu2+-doped CdTe1-xSex alloy nanocrystals (NCs) were successfully synthesized by the wet chemical method. The morphology and chemical compositions of the synthesized NCs were assessed by transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The structural and optical properties were characterized by X-ray diffraction (XRD), absorption spectroscopy (Abs), photo-luminescence (PL) spectroscopy, PL-decay lifetime. With the Cu2+ dopant concentration in the range of 0.5-5% and x of 0.5 in the precursors, the fabricated Cu2+-doped CdTe1-xSex NCs exhibited the dual emissions in the visible window at about 665 nm and near infrared window ranging from 830 to 840 nm which correspond to the excitonic emission of CdTe1-xSex NCs and Cu2+ dopant ions, respectively. With the increase in dopant concentration, the fluorescence lifetime of Cu-doped CdTe0.5Se0.5 NCs significantly improved (up to mu s) and the lattice constant of NCs decreased. By varying x from 0 to 1.0, both excitonic and dopant emissions of Cu-doped CdTe1-xSex NCs could be tuned in a wild range from 758 to 563 nm and from 918 to 748 nm, respectively. Interestingly, the crystal structure of these NCs changed gradually from the zinc blende (ZB) to wurtzite (WZ) structure when x increased. The results revealed that the dual emission, fluorescence lifetime and crystal structure of the Cu-doped NCs could be controlled by varying dopant concentration and chemical composition of the host.