Preparation And Performance Of Nitride Based Luminescent Materials For White LED

Solid-state lighting based on LED has gained widespread popularity in real life due to its smaller size,higher efficiency,longer lifetime and lower energy consumption compared to conventional light sources.For phosphor-converted WLED devices,the phosphor material is an important component that directly affects the relevant luminescence performance.Although there are suitable phosphors of various colors on the market,there are still some problems such as low CRI,high CCT and poor thermal stability,etc.For CRI and CCT,orange-yellow phosphors and red phosphors excited by blue light and trichromatic phosphors excited by near-UV chips can reduce the CCT and improve the CRI;for the problem of poor thermal stability,nitride substrates with dense spatial structure are selected for the study.Based on the above ideas,by modifying the existing phosphors or developing new phosphors to improve the CRI,CCT,and thermal stability of WLED will be beneficial to obtain high-quality white light.The main research and results of this thesis are as follows:1.Ca-α-SiAlON:Eu²⁺orange-yellow luminescent material was prepared via high-temperature solid-phase reaction（pressurized sintering）.The results showed that Ca-α-SiAlON:Eu²⁺could emit orange-yellow light around 590 nm under blue light excitation,and the regulation of emission wavelength could be achieved by adjusting the Al/Si ratio,and the increase of red light component of the yellow phosphor for blue light excitation would be beneficial to reduce the color temperature.At the same time,the phosphors with good dispersion of about 1μm particle size were successfully obtained by the solid-phase method combined with gravity sedimentation,which will expand the practical applications of Ca-α-SiAlON:Eu²⁺in automotive lighting and smart lighting.2.The CaAlSiN₃:Eu²⁺red phosphor was prepared by pressurized sintering.The asymmetric broadening of CaAlSiN₃:Eu²⁺phosphor emission spectrum toward the short wavelength direction was successfully achieved by CaAlSiN₃-Si₂N₂O binary solid solution,which will help to improve the problem of large emission wavelength of CaAlSiN₃:Eu²⁺phosphor in lighting applications.The multifaceted solid solution Ca_0.9-ySr_yAl_0.9Si_1.1N_2.9O_0.1:Eu²⁺was further prepared and investigated,and the results showed that the emission intensity and wavelength can be beneficially modulated within a certain range by solid solution.By prepared red-emitting materials and commercial green phosphor packaging on the blue light LED chip,the high color rendering index warm white light（CRI=89.3,CCT=4000 K）can be obtained.3.Eu²⁺-doped Sr₂BN₂Cl blue luminescent material was prepared by conventional high-temperature solid-phase reaction.Sr₂BN₂Cl:Eu²⁺exhibits a broadband absorption band in the near-UV region with an emission peak near 450 nm.Sr₂BN₂Cl:Eu²⁺fluorescent materials have good thermal stability,maintaining 87.4%and 100%of the room-temperature intensity at 150 and 250°C,respectively.The high structural rigidity of the Sr（N,Cl）₆ octahedral co-edge connection and the high-temperature re-release of electrons trapped in the material due to defects are responsible for its good thermal stability.WLED devices packaged with Sr₂BN₂Cl:Eu²⁺blue fluorescent material,commercial green phosphor,and commercial red phosphor show low color temperature（CCT=3190 K）and high color rendering index（CRI=92.0）.