The Investigation Of Preperation And Photoluminescenc Of Si-N Containing Phosphors Applied For White LED

The early arrival of energy crisis has made the low-carbon economy become the mainstream. As green light, white light emitting diodes (LED) have attracted much attention. With the appearance of the new requirements for phosphors used on high power white LED, the phosphors containing Si-N covalent bond are increasingly becoming the new highly efficient fluorescent material of white LED because of their excellent properties, such as good thermal stability.This thesis will focus on the phosphors containing Si-N covalent bond used on white light LED, especially the enhanced luminescence of the phosphors containing Si-N covalent bond by ionic co-doped, changement of luminescence properties for phosphors introduced Si-N covalent bond, the exploratory preparation of the phosphors containing Si-N covalent bond and thermal stability of phosphors. The main achievements obtained include:A. SrSi2O2N2: Eu²⁺ green phosphors applied for white LED are successfully prepared, which can be effectively excited by ultraviolet (UV) - visible light (300⁴60 nm) and yield yellowish green emission with a single, intense, broad band centred at around 538 nm. With an increase in the Eu²⁺ concentration, the emission intensity enhances and the emission band shifts to a longer wavelength. The addition of Mn²⁺ and Pr³⁺ in the Eu²⁺ site in SrSi2O2N2 remarkably enhance the luminescent intensity by the factor of 364 % and 268 % for Mn²⁺ and Pr³⁺, respectively. Partial substitution of Sr²⁺ by Ba²⁺ results in a red-shifted Eu²⁺ emission.B. Photoluminescence (PL) and colorimetric properties of white-light emission SrAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphor are tuned effectively through incorporating Si-N bond to the host in the form of Si3N4. Phenomena of distinct red-shift, broadening of blue band emission for Eu²⁺ and enhancement of yellow band emission for Mn²⁺ are observed with the increase of Si-N content. Eventually, a white emission with CIE Chromaticity coordinates (0.287, 0.337), color rendering index (CRI) 78.3 and color temperature (8739 K) for SrAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphor are achieved upon optimization to a suitable amount of Si-N.C. We research the exploratory preparation of Ca2Si5N8:Eu²⁺ red phosphors applied to white LED. On the basis of the X-ray diffraction patterns about our phosphor samples, the main phase is Ca2Si5N8 with the second phase Si3N4. When these phosphor samples are excited by 365nm, they emit 450 nm and 600 nm which ascribe to the Eu²⁺ transition in Si₃N₄ and Ca2Si5N8, respectively. At last, our phosphor samples emit white light because of the overlap of blue and orange light.D. The phosphors containing Si-N covalent bond have small thermal quenching.The investigation of preperation and photoluminescenc of the phosphors containing Si-N covalent bond in this paper shows potential application in white LED solid state lighting.