Spectroscopic properties of Dy 3+ doped ZnO for white luminescence applications.

Undoped and Dy3+ (0.25, 0.5, 0.8 and 1.5at.%) doped ZnO were elaborated by solid-state reaction method. The ZnO:Dy3+ 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 Dy3+ content, indicating the substitution of these ions into the ZnO lattice. Raman study indicates the good crystallinity of all ZnO:Dy3+ samples and confirms the substitution of Zn2+ by Dy3+ . The band gap energy was found to increase then decrease with Dy content. The PL excitation spectra (PLE) of Dy3+ showed six excitation bands with hypersensitive at 346nm (6 H15/2 →6 P7/2 ). PL spectra show principally three emission bands relatives to4 F9/2 →6 H15/2 (476nm),4 F9/2 →6 H13/2 (567nm) and4 F9/2 →6 H11/2 (658nm) transitions. The concentration dependency of PL intensity indicates a quenching for Dy3+ concentration above 0.5at.%. The PL lifetime of4 F9/2 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:Dy3+ can be useful for white luminescence applications.