Ce:YAG phosphors used in white LED backlit LCD displays suffer from two major issues: the phosphor powder is too large for next generation microLED display technology, and there is a lack of red in its emission spectrum. To address this, Ce:YAG based nanophosphors were synthesized using the glycothermal method. They were found to contain ~10x higher concentrations of octahedrally coordinated Al atoms compared to bulk Ce:YAG, confirmed by NMR spectroscopy. Photoluminescence and photostability were found to be enhanced with the growth of an intrinsic shell layer, made using a two-step growth process. Shell thickness was controlled by the addition of intrinsic precursor material as a ratio of the initial precursor concentration, denoted as the shell-to-seed ratio (SSR). The absorption spectra of Ce:YAG could be tuned up to 40 nm with the addition of Mg-Si pairs. An enhancement of Ce:YAG nanophosphor luminescence was seen when the reaction temperature was slightly elevated, attributed to increased precursor reactivity due to the higher kinetics of precursor ligand cleavage. The introduction of Mn2+ as a co-dopant was found to provide a red component to the Ce:YAG emission spectrum. XRD structural analysis indicated that Mn2+ should preferentially occupy the Y site, though the 594 nm emission characteristic of 4T1(4G) 6A1(6S) transitions in octahedral co-ordination was observed. Mn2+ atoms which occupy Al octahedral sites are well supported for luminescence due to the high density of octahedral sites present after gycothermal synthesis. Mn2+ emission was enhanced using Si4+ as a charge compensator, and further enhanced with the addition of an intrinsic shell layer. Non-radiative energy transfer of Ce to Mn2+ was observed, indicating that the parity allowed 5d 4f transition of Ce acts as an effective sensitizer for Mn2 luminescence. Glycothermal synthesis was found to preserve the luminescent trivalent and divalent oxidation states of Ce and Mn, respectively. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27349 |
| Date | January 2022 |
| Creators | Peter, Samuel |
| Contributors | Kitai, Adrian, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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