SINGLE-PHASED WARM WHITE-LIGHT-EMITTING ZnO:Al PHOSPHOR FOR SOLID-STATE LIGHTING APPLICATIONS

Abstract

Al-doped ZnO powder was successfully fabricated by a surface diffusion method. The characterization of the crystal structure shows that the diffraction peaks of the hexagonal crystal phase of ZnO shifted to a larger angle of 2q, following by the decrease of cell volume of ZnO:Al powder after using the thermal energy to diffuse Al³⁺ ions into the host lattice. The photoluminescence spectra of obtained products showed that when the temperature increases, a higher concentration of Al³⁺ ion considerably diffuses into the ZnO host lattice and creates many defects following by a red shift of emission band in the visible region. By optimizing the synthesis condition, the PL of ZnO:Al (3%mol) sample annealed at 800 ° C for 2 hours shows the highest emission intensity peak at 542 nm with a full width at half maximum (FWHM) bandwidth of ~ 186 nm, covering the whole visible region. After coating, ZnO:Al phosphor on a UV-LED chip, the as-received LED exhibits a warm white light emitting with the correlated color temperature (CCT) of 4067 K and a high color rendering index (CRI) of 87. Therefore, ZnO:Al phosphors show a great potential to be used in the manufacture of white light-emitting diodes.