Near UV excitable warm white light emitting Zn doped γ-Ga2O3 nanoparticles for phosphor-converted white light emitting diode

Abstract

Optical properties of Zn doped γ-Ga2O3 nanoparticles are investigated for the generation of white light, using near UV LED chip for phosphor-converted WLED (pc-WLED) application. Sol-gel combustion technique is adopted for the synthesis of Zn doped γ-Ga2O3 nanoparticles. The synthesized Ga2O3 nanoparticles are formed as metastable γ-phase with the face-centred cubic crystal structure. The structural stability is maintained up to 15 mol% doping of Zn ions. Formation of aggregated ultrafine particles of undoped and Zn doped γ-Ga2O3 with size less than 4 nm is found from TEM results. Doping of Zn ions has altered the optical band gap of γ-Ga2O3, and it varies from 4.13 to 3.97 eV. Broad visible emission in the wavelength range of 400–600 nm is observed and broadening of emission band increases after Zn doping. Formation of high defect concentration and smaller size of 10 mol% Zn doped γ-Ga2O3 nanoparticles resulted in higher emission intensity. Wide photoluminescence excitation band from 330 to 475 nm suggests that wide visible emission can be obtained from Zn doped γ-Ga2O3 nanoparticles with the excitation of both near UV and blue light. The bi-exponential behavior of PL decay curves of emission bands at the blue and yellow region indicated the complicate luminescence process of Zn doped γ-Ga2O3. The estimated lifetime of blue emission varies from 30 to 37 ns and of yellow emission varies from 54 to 62 ns. Under the excitation of 375 nm LED chip, warm white light emission with CIE color coordinates of (0.42, 0.33), color rendering index of ~ 87 and CCT of 2365 K is obtained for 10 mol% Zn doped γ-Ga2O3 nanoparticles which exemplifying its potential application in pc-WLED fabrication.