Abstract
Y3Al5O12 (YAG) nanocrystals have been synthesized by a modified solvothermal method (300°C) allowing the incorporation of cerium ions in much larger proportion (up to 30 mol.% with respect to yttrium ions) than ever published. The reasons are the nanometric size of the produced nanocrystals, allowing to accommodate Ce3+ ions in the rigid YAG structure thanks to the presence of local distortions, and also the soft synthesis route, at low temperatures and far from the thermodynamic equilibrium, which favors the cerium insertion. As a consequence, Ce3+ photoluminescence spectrum can be tuned with the doping concentration, from 541 nm for low Ce3+ concentration to 580 nm for a cerium concentration of 30 mol.%. The internal quantum yield reaches 40 ± 5% before decreasing due to concentration quenching. The nanocrystal brightness, which combines the internal quantum yield and the cerium concentration, has been found optimal for a doping of 2 mol.% Ce3+.
Highlights
Ce3+-doped yttrium aluminum garnet (Y3Al5O12:Ce3+, YAG:Ce) is a well-known luminescent material, studied both at the macroscopic scale and at the nanometric scale for artificial lighting generation as phosphor-converted white LEDs (Ryu and Kim, 2010; Cantore et al, 2016)
We report the study of YAG:Ce nanocrystals brightness as a function of cerium concentration
We highlight the drastic discrepancy in terms of cerium insertion between cm- and micron-sized YAG crystals (0.2 and 3 mol.% resp.) and our YAG nanocrystals (30 mol.%)
Summary
Ce3+-doped yttrium aluminum garnet (Y3Al5O12:Ce3+, YAG:Ce) is a well-known luminescent material, studied both at the macroscopic scale (large single crystals, ceramics, micron-sized powder, films) and at the nanometric scale (nanocrystals) for artificial lighting generation as phosphor-converted white LEDs (pc-wLEDs) (Ryu and Kim, 2010; Cantore et al, 2016). YAG:Ce remains the major phosphor used in pc-LEDs to partially convert blue light emitted from GaN/InGaN diode into yellow light. The use of the resin, which deteriorates over time under intense blue light excitation, induces a color drift of the pc-wLEDs, (Deng et al, 2019) while the micron-sized YAG:Ce particles generate light scattering that reduces the external efficiency of the pc-wLED devices. These drawbacks have encouraged researchers and industrials to find alternative materials and shaping (transparent/translucent ceramics, nanocrystals), allowing better ageing properties and
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