Optical properties of CdS nanocrystals doped with zinc and copper

Cadmium-sulfide nanocrystals are produced by the colloidal method. Doping with zinc and copper is conducted during nanocrystal growth. The optical absorption and photoluminescence spectra are studied. The maximum concentration of the optically active copper impurity is determined from a shift of the fundamental absorption edge to lower energies. It is shown that the long-wavelength luminescence of CdS and CdS:Zn nanocrystals is defined by optical transitions at donor–acceptor pairs. In CdS:Cu nanocrystals, optical absorption and photoluminescence in the visible spectral region are defined by recombination transitions involving the ground state of Cu$_{\operatorname{Zn}}^{2+}$ ions. The infrared absorption and photoluminescence of CdS:Cu quantum dots are defined by intracenter transitions within Cu$_{\operatorname{Zn}}^{2+}$ ions.