(The) luminescence properties and energy transfer mechanism of novel alumino-silicate based phosphors synthesized by wet-chemical reaction method

Abstract

Light-emitting diode (LED) with phosphor materials to generate white light is the present focus of research in the lighting industry because of their benefits in terms of energy saving, reliability, maintenance and safety. Currently, white LEDs have already begun to replace conventional lighting source (incandescent bulbs and fluorescent lamps). The present way of producing a white light is the combination of a blue LED chip with yellow-emitting $Y_3Al_5O_{12}:Ce^{3+}$ (YAG:Ce) phosphor, but this method cannot fulfill the requirement for general illumination and other applications due to the lack of red component of YAG:Ce phosphor. In order to solve this problem, the white LEDs based on a UV-LED chip coated with three red, green, and blue emitting phos-phors were introduced and have come into the spotlight. However, this combination has low luminescent effi-ciency owing to strong reabsorption of blue light by the red and green phosphors. As an alternative plan, sin-gle-phased white-emitting phosphors are introduced. This system has high luminous efficiency and excellent color rendering index. Therefore, recent researches have focused on finding phosphors which can be excited by UV sources. The performances of WLEDs strongly depend on the luminescence properties of phosphors used. So, as conversion luminescent materials in WLEDs, phosphors need to have high conversion efficiency, appropriate emission colors, and high stability. For these reasons, recently aluminosillcate-based phosphors have drawn much attention for their excellent luminescence properties such as stable crystal structure, high chemical and physical stability. Therefore, as the motivation of research topic, alumino-silicate based novel blue- and white-emitting phosphor are synthesized and studied in this thesis. To the best of our knowledge, there has been no reported study on $Na_{0.34}Ca_{0.66}Al_{1.66}Si_{2.34}O_8$ (NCASO), which is included in the plagioclase feldspar crystal structure, as...