Preparation Of Phosphor Materials For White LED And Study On Luminescence Mechanism

White light LEDs(WLEDs)have been widely used in various display and lighting devices due to the pursuit of white light devices with long life,low cost,and excellent optical performance.However,commercially available green phosphors for backlighting are limited by their half-peak width value(FWHM)and emission peak level,making it difficult to achieve large color gamut values.To improve the color gamut of LED backlighting,researchers are working to develop a new class of narrowband phosphors with high quantum efficiency and excellent chemical and thermal stability.As the heaviest metallic element in nature,uranium is used both as nuclear fuel to provide clean energy in the form of nuclear power and to create weapons of mass destruction.Although uranyl ions have excellent luminescent properties,research on the luminescent properties of uranyl ions has been limited.On the other hand,for WLEDs for lighting,commercial WLEDs are based on blue chips such as In Ga N combined with yellow phosphors YAG:Ce3+ to emit white light.The lack of red light component in this light-emitting method leads to the lower color rendering index and higher color temperature of WLEDs,which are not suitable for warm white indoor lighting.The specific research is as follows.Aimed to solve the problems of existing white LEDs,this paper designs and studies the light-emitting materials of LEDs for backlighting and lighting,respectively.The main work is as follows:1.Uranium phosphate crystals(HUP-2)were synthesized by a mild hydrothermal reaction,and their structures were resolved by single-crystal diffraction,and the high phase purity of HUP-2 was verified by electron microscopy and powder diffraction(XRD).Due to the rigid and symmetric structure of HUP-2,HUP-2 possesses a broad excitation band with a narrow emission peak(FWHM = 43.15 nm)and shows an internal quantum efficiency close to 100 %(93.66 %)and a high external quantum efficiency(82.05 %).Besides,HUP-2 was found to exhibit excellent chemical stability,irradiation resistance,and thermal stability.To verify the application potential of the synthesized uranium phosphate crystals(HUP-2),LEDs with a wide color gamut of107.6 % for backlighting were prepared by combining HUP-2,commercially available blue chips,and red phosphors.2.A Metal-Organic gel material(YTU-1000)was synthesized by a mild solvothermal reaction and was found to possess high internal quantum efficiency(95.45 %),external quantum efficiency(88.15 %),and aggregation-induced fluorescence(AIE)properties.To explain the mechanism of the AIE effect,the structure of the material was verified by powder diffraction,infrared spectroscopy,BET,SEM,and X-ray spectroscopy,and the fluorescence data were collected by photoluminescence spectroscopy,which proved that the dense and non-porous structure of the material is the fundamental reason for the high internal and external quantum efficiency of the material.In addition,the material was tested for water stability and proved to have excellent chemical stability.By combining YTU-1000,blue chips,and commercially available red phosphors,the prepared LEDs exhibited a color rendering index of 88.2 and a warm white light characteristic with a color temperature of 3736 K.