Structural, luminescence and photoconversion properties of Lu3Al5O12:Ce single crystalline film phosphors for WLED application

Abstract

This work focuses on the detailed investigation of structural, luminescence and photoconversion properties of Ce doped Lu3Al5O12:Ce (LuAG:Ce) single crystalline films (SCFs) grown using the Liquid Phase Epitaxy (LPE) method onto Y3Al5O12 (YAG) single crystal substrates as promoting converting film material for high-power WLED. The structure and chemical composition were analyzed using X-ray diffraction (XRD) and High-Resolution Scanning Transmission Electron Microscopy (HR-STEM). HR-STEM analysis and composition analysis revealed an interface with high structural quality including the formation of a transition layer with a 6 nm thickness between LuAG:Ce SCF and YAG substrate. The composition of this layer changes smoothly from YAG substrate towards LuAG:Ce SCF, and after equalizing the SCF/substrate misfit, stable LuAG:Ce film growth is observed. The optical characterization of LuAG:Ce films were performed using absorbance, cathodoluminescence and photoluminescence emission/excitation spectra and photoluminescence decay lifetime, as well as photoconversion measurements under blue, LED excitation. The corresponding color coordinates, color temperatures, color rendering index and luminous efficacy of white light sources based on blue LEDs and LuAG:Ce film converters with thicknesses in the 19–160 nm range were estimated and best characteristics are achieved for the 92 µm thick sample.