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The phosphor was surface-treated with oxide by the Sol-Gel method. On the surface of the phosphor, we succeeded in modifying the surface of the phosphor by attaching nanoparticles with a size of 20-50 nm to the surface.
In addition, the synthesized phosphors for LED and commercial YAG phosphors were also added with oxide nanoparticles on the surface in the same way as for PDP(Plasma Display Panel) phosphors to improve the properties of phosphors.
The surfaces of the uncoated phosphors and the coated phosphors in the SEM picture shows a clear difference, and it shows that oxide nano-particles are attached to the surface of each phosphor that has been surface-treatedby the Sol-Gel method. It was confirmed through EDS and XPS whether the attached nano-particles match the component in the experiment. The Si, Y, Ti and Al peaks and the result of the component ratio table prove that the particles on the surface of the phosphor shown in the SEM picture are SiO$_2$, Al$_2$O$_3$, Y$_2$O$_3$, TiO$_2$, etc.
In order to evaluate the effect of oxide nano-particles on the characteristics of the surface of the phosphor, a test panel was prepared for the PDP(Plasma Display Panel) VUV-phosphor and a white LED device for the LED phosphor was fabricated.
Both the phosphors surface-treated with SiO$_2$ or Al$_2$O$_3$ and the phosphors surface-treated with two oxides(SiO$_2$, Al$_2$O$_3$) one after the other were used on a test panel to investigate the luminescence characteristics in VUV. The luminance was higher than that of the red phosphor. On the other hand, the luminance increased when Al$_2$O$_3$ was coated and when Al$_2$O$_3$ and SiO$_2$ were double coated, while the luminance decreased slightly in the case of SiO$_2$ coating. Also, in the case of the green phosphor, when Al$_2$O$_3$ and SiO$_2$ were double coated, a dominant increase in luminance was shown. Unlike red and blue, the green phosphor showed a very high luminance increase when coated with Al$_2$O$_3$. In general, when Al$_2$O$_3$ was coated, the optical properties were better than others.
In addition, in the case of the LED device, the optical properties were improved when SiO$_2$ was coated. However, in the lifetime test of the white LED device, there was no significant difference between the coated LED device and the uncoated LED device, which is thought to be because the stability of the YAG phosphor has already been secured.
The increase in transmittance due to the difference in refractive index, reduction of non-radiative recombination through surface defect level, and passage of emitted light through nano-particles on the surface can be considered as causes of the increase in luminance for surface-modified by nano-particles shown in this study, but a clear cause has yet to be identified. A more detailed study under various conditions and a more clear luminance increase mechanism are needed.
지도교수: 손상호