Enhancement of the visible luminescence from the ZnO nanocrystals by Li and Al co-doping

Nanocrystals of ZnO, doped with aluminum and lithium, were synthesized by chemical co-precipitation from an aqueous solution mixture of Zn(NO)3, AlCl3 and LiCl. With an aim to produce strong white luminescence, the intensity of the visible luminescence was tailored as a function of dopant concentration. We observed a significant enhancement of the yellowish-white photoluminescence from ZnO nanocrystals due to co-doping with aluminum and lithium. The luminescence intensity increases and the peak position shifts to lower wavelength with increase in the dopant concentration. Although the exact mechanism of the enhancement of the luminescence could not be established, still a possible shallow donor-to-deep acceptor recombination was proposed.