Yellow and warm white light emitting Zn doped Y_2O_3 for near UV excitable phosphor converted WLED

摘要

Optical properties of Zn doped Y2O3 microsheets prepared by sol-gel combustion method have been investigated and their application in phosphor converted white LED has been examined. The formation of single phase, well crystalline cubic Y2O3 is confirmed from powder XRD results. Effective substitution of Zn in Y2O3 crystal lattice is inferred from shifting of diffraction peaks. SEM images have showed that undoped as well as Zn doped Y2O3 formed as microsheets. Doping of Zn enhanced the growth of the sheets and its length increased from 1.5 to 19 mu m. Development of structural disorder in Y2O3 crystal structure after Zn doping and confirmation of the conserved cubic structure of Zn doped Y2O3 without any secondary phase have been revealed from micro-Raman spectra. The optical band gap of Y2O3 has been altered after Zn doping and it is found to be decreased from 5.6 to 5.22eV as increasing Zn concentration. Both undoped and Zn doped Y2O3 showed a broad visible emission from blue to green region due to various defects and impurities present in it. Broad PL excitation spectrum inferred the possibility to attain the visible emission under the excitation of light with wide range of wavelength from near UV to blue region. Excitation of pure Y2O3 under near UV (375nm) LED chip lead to the emission of yellow light whereas Zn doped Y2O3 emitted warm white light with color coordinate of (0.42, 0.35), colour rendering index of 77.6 and correlated color temperature (CCT) of 2840K. Hence, Zn doped Y2O3 discussed in the present work can be a better replacement for various rare earth doped phosphors in the application of phosphor converted WLED (pc-WLED).