Preparation And Properties Of Phosphor-in-glass Thick Films For Warm White LED

White light-emitting diode?LED?,as a new forces of luminescent field,has played a crucial role in applications of interior lighting,automobile headlight,display backlight,and landscape lighting due to its excellent properties,such as,energy-efficient,environment-friendliness,small volume,long lifetime and so on.Currently,the combination of InGaN blue chips and Ce³⁺:Y₃Al₅O₁₂?Ce-YAG?yellow phosphors using silicon resin is the most commonly used way to achieve white light emission in commercial white LED.However,silicon are easily suffering from aging and yellowing due to poor thermal conductivity,which further leads to a decline in luminous efficacy and even lifetime of high-power white LEDs.Besides,due to the lack of red light emission,the resulting LED devices emit white light of poor color rendering index and color temperature.To solve the above problem,inorganic glass is employed as encapsulating material to substitute for the traditional organic resin.Meanwhile,red or orange phosphors are more appropriate to be embedded into fluorescent layer to achieve the warm white emission of LED devices.In this work,two glass systems was chosen to fabricate a variety of PiG thick films via multilayer screen-printing and subsequent heat treatment.The optimum condition and simple technology process of PiG thick films with high optical properties are obtained.Notably,the PiG thick films based white LEDs have desirable potential for application in the market,and show excellent color rendering.In addition,the structural,micro-structures and optical properties of PiG thick films are systematically investigated with the help of X-ray diffraction,scanning electron microscopy,transmission spectrum and luminescence spectra.The main research results have been summarized as follow:?1?Ce-YAG PiG thick films were successfully fabricated via screen-printing and subsequent low-temperature sintering in 58TeO₂-8B₂O₃-16ZnO-12Na₂O-6Al₂O₃ glass matrix.The structural,micro-structures and optical properties of Ce-YAG PiG thick films at different temperatures was studied.In addition,the PiG thick films were utilized to fabricate a white LED device,the thickness dependence of optical parameters were discussed in detail.Notably,a LE of 78.7 lm/W and excellent color quality are achieved at the film thickness of 68.3?m.?2?Eu²⁺:Sr₂Si₅N₈?Eu-SSN?/Ce-YAG PiG thick films were successfully fabricated via screen-printing and subsequent low-temperature sintering in 35P₂O₅-47ZnO-6Na₂O-6Li₂O-6BaO glass matrix.The XRD,SEM and PL results confirmed that the introduced commercial phosphor crystals dispersed uniformly in phosphate glass matrix.The chromaticity of as-encapsulated white LED devices was easily tuned by adjusting the weight ratio of red to yellow phosphors.When fixed red to yellow phosphors ratio of 5:95,an optimized warm white light was finally achieved with a LE of 72.1 lm/W,a Ra of 82.5 and a CCT of 5612 K.?3?Ce-YAG,Eu²⁺:Sr₃SiO₅?Eu-SSO?,and novel Eu-SSO/Ce-YAG PiG thick films were successfully fabricated via screen-printing and subsequent low-temperature sintering in 35P₂O₅-47ZnO-6Na₂O-6Li₂O-6BaO glass matrix.The Eu-SSO phosphor concentration dependence of colourimetry parameters were studied in detail.Notably,we fabricated a warm white LED with a LE of 73.5 lm/W,a CCT of 5568 K,and a Ra of 81.6.