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)

Using low-temperature (650¢J) Ce3+:YAG doped glass (LTCeYDG) phosphor layer instead of conventional Ce:YAG doped silicone phosphor layer applied to high-power phosphor-converted white-light-emitting diodes (PC-WLEDs) is demonstrated.The glass transition temperature (Tg) of silicone is 150¢J but glass is 750¢J,it shows the glass were employed in high power LED than silicon. The uniformity of phosphor powder doped glass is an important item to discriminates between good and bad. Quantize the uniformity of glass phosphor by image processing software and Distribution Uniformity (Du). Calculate the uniformity of phosphor powder mix with glass powder which has different particle size and measurement optical properties of glass phosphor which has different uniformity. The Du of glass phosphor are 64.46%, 84.65%, 85.24% , 91.85% and the quantum efficiency are 18.49%, 28.31%, 29.73%, 28.56% ,respectively. By using Ceramic tube and low temperature glass powder sintering glass phosphor is a new fabrication. Compare with last fabrication, new fabrication reduce 100¢Jfabrication temperature from 750¢J to 650¢J, 70% material savings and high luminous efficiency. The quantum efficiency and lumen per watt were improved about 7 percentage point from 22.3% to 29.1% and 4.2 lm/W from 36.4 lm/W to 40.68 lm/W. We used the XRD to analyze the glass phosphor of last fabrication and new fabrication and the results show that the higher thermal stress destroys the structure of YAG, lower fabrication temperature used to get higher luminous efficiency.