Spectroscopic properties of Dy doped ZnO for white luminescence applications.

Undoped and Dy (0.25, 0.5, 0.8 and 1.5at.%) doped ZnO were elaborated by solid-state reaction method. The ZnO:Dy samples were characterized using X-ray diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy and photoluminescence (PL). The XRD analysis confirms the wurtzite structure of ZnO. A slight shift to lower angles, of the (101) peak, is seen with Dy content, indicating the substitution of these ions into the ZnO lattice. Raman study indicates the good crystallinity of all ZnO:Dy samples and confirms the substitution of Zn by Dy. The band gap energy was found to increase then decrease with Dy content. The PL excitation spectra (PLE) of Dy showed six excitation bands with hypersensitive at 346nm (H→P). PL spectra show principally three emission bands relatives to F→H (476nm), F→H (567nm) and F→H (658nm) transitions. The concentration dependency of PL intensity indicates a quenching for Dy concentration above 0.5at.%. The PL lifetime of F metastable state was measured and discussed for all Dy content in ZnO. The temperature dependency of PL intensity is investigated for ZnO:Dy (0.5%) sample and the activation energy is determined. The CIE chromaticity color coordinate shows that ZnO:Dy can be useful for white luminescence applications.