Green phosphor thin films with different silica resin/phosphor mass ratios and phosphor particle sizes were prepared by the hot pressing method. A 405 nm near-ultraviolet light-emitting diode (LED) chip was used to package the laminated white LED (WLED), and the correlated color temperature, luminous efficiency of radiation, light color uniformity, and color coordinate of the laminated WLED were obtained. An increase in the mass ratio and decrease in particle size can effectively affect the scattering coefficient of phosphor photons and the efficiency of the absorption–excitation–emission process, increasing the efficiency and light color uniformity of phosphor thin films and laminated WLEDs. By comprehensive evaluation of various light color parameters, a laminate was prepared with a mass ratio of silica resin/phosphor = 6 : 0.75, and the optimum value of the WLED was obtained. According to the IES TM30 standard, its R_f reached 92, R_g reached 101, and R_g and color distortion icons showed increased saturation for green color. Its luminous efficiency of radiation value of 270.21 lm W⁻¹, correlated color temperature of 4423 K, and neutral white characteristics indicate that it is a device suitable for lighting applications.

Ce³⁺, Pr³⁺ co-doped Lu₃Al₅O₁₂ (Ce, Pr:LuAG) single crystals and ceramics were prepared using the optical floating zone (OFZ) and reactive vacuum sintering methods, respectively. The microstructure, photo- (λ_ex = 450 nm), and radio-luminescence (under X-ray excitation) performance, as well as scintillation light yield (LY, under γ-ray, ¹³⁷Cs source) of both materials, were investigated and compared. Ce, Pr:LuAG ceramics had an in-line transmittance of approximately 20% in the visible light range, while the analogous crystals were more transparent (~65%). The X-ray excited luminescent (XEL) spectra showed the characteristic Ce ³⁺ and Pr³⁺ emissions located at 310 nm, 380 nm, and 510 nm. The highest LY of the Ce, Pr:LuAG ceramics reached 34,112 pho/MeV at 2 μs time gate, which is higher than that of a single crystal. The ratio of LY values (LY2/LY0.75) between shaping times of 0.75 μs and 2 μs indicated a faster scintillation decay of ceramics regarding single crystals. It was ascribed to the lower effective concentration of luminescent activators in single crystals because of the coefficient segregation effect.

Red phosphor thin films (PTFs) with different MgO nanoparticle concentrations for near-ultraviolet (NUV) LEDs were prepared based on their strong scattering effect; red LEDs and laminated white LEDs were packaged further. SEM and XRD showed that CaAlSiN₃:Eu²⁺ (CASN) and MgO nanoparticles were uniformly distributed in silicone resin and their crystal structure remained unchanged. The phosphor conversion efficiency (PCE) had a maximum value of 83.15% when the MgO nanoparticle concentration was 15 wt%. An increase of concentration can improve the spatial distribution uniformity of photonics for 410 nm, 627 nm and 660 nm. Fluorescence lifetime showed that the value is positively correlated with concentration change. The packaged red LED luminous flux reaches a maximum of 20.337 lm at a concentration of 15 wt%. The laminated white LED showed that the MgO nanoparticle concentration can be used to adjust the correlated color temperature (CCT) from 4322 K to 1987 K. Under similar CCT, the red phosphor concentration is only 1.83 wt%, the dosage is reduced by 56.12%, and the corresponding luminous efficiency of radiation (LER) and luminous efficiency (LE) are 296.03 lm W⁻¹ and 73.72 lm W⁻¹ respectively. The increase was 11.42%, the decrease was 10.14%, the color rendering index (CRI) increased from 90.6 to 91.8, and CCT uniformity increased from 82.04% to 89.27% with an increase of 8.81%. Research shows that MgO nanoparticles have potential application value in the preparation of high-quality white LEDs.

We prepared blue, green and red phosphor thin films (PTFs) with different phosphor concentrations used for near-ultraviolet (NUV) LEDs respectively, and then investigated their spectral re-absorption/excitation/emission process. The functional relationship between optical powers and concentrations were established by using the exponential equation. The relationship between the spectral deformations and concentrations were evaluated by the correlation coefficient. Based on NUV LED chip, eight package structures of white LEDs were prepared. The luminous efficiency (LE) of white LED based on Blue/Green/Red@NUV laminate structure reached 85.48 lm/W, which was 27.7% higher than that of hybrid structure, correlated color temperature (CCT) was 3518K, R_f was 83, R_g was 106, and when hybrid structure thickness was reduced to one-third points, the LE increased by 21.5% to 81.36 lm/W, CCT was 4200K, R_f was 93, R_g was 101, CCT uniformity test showed that the uniformities of laminated and hybrid structures were 80.06% and 96.91% respectively. The results showed that the laminated structure was beneficial to improve the LE, while the hybrid structure had the advantage of uniformity improvement and spectrum continuity due to multi-particle scattering and spectral deformation of the phosphor.

利用热压法将TiO2微粒掺入至YAG:Ce荧光粉和硅树脂中制备出远程荧光粉膜并封装成白光发光二极管(LED)器件, 通过荧光粉相对亮度仪、双积分球测试系统和可见光光谱分析系统对样品的光色性能及机理进行了研究. 结果表明: TiO2的散射效应能够显著提高蓝光的利用率和黄光的透射强度, 白光LED器件的光通量在TiO2浓度为0.966 g/cm3 时达到最高值415.28 lm(@300 mA, 9.3 V), 提高了8.15%, 相关色温从冷白6900 K逐渐变化至暖白3832 K. TiO2的掺入不仅提高了远程荧光粉膜的发射强度和白光LED器件的光通量, 同时能调控其相关色温.

A series of apatite-type Sr3LaNa(PO4)3F:Ce3+, Tb3+ phosphors were synthesized via high temperature solid-state reaction method. X-ray diffraction (XRD), scanning electron microscopy (SEM), the photoluminenscence excitation (PLE) spectra and photoluminescence (PL) spectra were used to characterize samples. And systematic study on micro-morphology, spectral luminescent properties and process of energy transfer in Sr3LaNa(PO4)3F:Ce3+, Tb3+ phosphors.The results show that Sr3LaNa(PO4)3F:Ce3+, Tb3+ phosphors with strontium apatite crystal structure, and the morphology is irregular. The optimum concentration of Ce3+ in Sr3LaNa(PO4)3F:Ce3+ was decided to be 0.04, and the emission peaks at 340 nm is due to the 5d→2F5/2 and 2F7/2 transitions of Ce3+. The PL spectra of Sr3LaNa(PO4)3F:Tb3+ phosphor excited by 253.7 nm presents green-emitting light centered at 543 nm. Effective energy transfer from the sensitizer Ce3+ to activator Tb3+ can be expected in the Ce3+ and Tb3+ co-doped phosphors Sr3La0.96-yNa(PO4)3F:0.04Ce3+,yTb3+. Based on the spectral analysis, The energy transfer efficiency from Ce3+ to Tb3+ reaches up to 78.6%. The energy transfer mechanism from Ce3+ to Tb3+ was via the exchange interaction. In Ce3+ and Tb3+ co-doped Sr3La0.96-yNa(PO4)3F:0.04Ce3+, yTb3+ phosphors, the chromatic coordinate was observed with increasing Tb3+ co-doping rate on moving from (0.2867, 0.2411) at y = 0.00 to (0.3267, 0.5845) at y= 0.40.