Synthesis And Luminescence Properties Of Anti-UV White Rare-Earth Organosilicon Phosphors

Near-UV white LED has become the first choice for LED healthy lighting owing to its high color rendering index,strong color reproduction ability and light color adjustability.Recently,lanthanide complexes have been one of the mainstream luminescent materials because they exhibit sharp and intense emission lines upon ultraviolet light irradiation.However,the complexes are easy to suffer from aging due to the long-term ultraviolet radiation applied in the near-UV LED.Organosilicon polymers have the advantages of extraordinary mechanical properties,high transmittance,excellent UV-aging resistance,good film-forming and high thermal stability.Therefore,organosilicon polymers and lanthanide complexes are combined to obtain the lanthanide complex-organosilicon hybrid material with both advantages,which provide us a new idea to solve the problems faced by the fluorescent materials used in the near-UV LED,such as UV aging and thermal degradation.Employing pre-coordination and subsequent polymerization,a series of bonded rare-earth organosilicon copolymers were copolymerized with different vinyl-functionalized complex monomers and polysiloxane prepolymer.Meanwhile,the copolymers were encapsulated to fabricate the LED devices and their actual performance were investigated.（1）The polysiloxane prepolymer was synthesized by the polycondensation between vinyltrimethoxysilane and diphenylsilanediol.Then Eu-complex was introduced into polysiloxane prepolymer to obtain the red organosilicon copolymer.The results of test and characterization show the copolymer with the molar ratio of 50:1 possesses optimal luminescence properties.When excited by 365 nm UV light,the copolymer exhibits strong red characteristic emissions of Eu³⁺ion in 612 nm,and the luminescence lifetime of 612 nm emission is 0.666 ms.TG-DTG analyses indicate the copolymer keeps stable up to 321℃.After 30-day UV aging test only shows luminance loss of 6%and power efficiency loss of 7.3%,so the UV-aging resistance of the copolymer is realized.（2）The green organosilicon copolymer was prepared by bonding the Tb-complex into polysiloxane prepolymer.When the molar ratio of polysiloxane to Tb-complex is 100:1,obtained copolymer has optimal luminescence properties.Under 365 nm excitation,the characteristic emission peak of Tb³⁺appears at 544nm.The coplymer can keep stable up to 466℃.Finally,after UV aging test,the LED fabricated with the Tb complex shows luminance loss of 63.7%,while the LED fabricated with the copolymer shows luminance loss of 17.7%,so the copolymer owes superior UV-aging resistance.（3）The blue light organosilicon copolymer was obtained by copolymerization between the Zn-MOF small molecule complex and polysiloxane prepolymer.The test results show that when excited at 365 nm,the copolymer exhibits a strong emission peak at 450 nm,which appears blue shift compared with the Zn-complex.The copolymer decomposes at 351℃.After UV aging test,the LED fabricated with the Zn complex shows luminance loss of 69.5%,while the LED fabricated with the copolymer shows luminance loss of 22%,indicating the UV-aging resistance of the copolymer is realized.（4）Through a self-made three primary colours matching program,the proportion of different complexes is designed.When the ratio of three primary colors is 1:6:3,the copolymer emitted near white light with the CIE coordinates（0.327,0.321）is obtained under 365 nm excitation.When the excitation wavelength shifted from 290 nm to 390 nm,the copolymer realizes a series of changes in the emission light from yellow to blue light.TG-DTG analyses indicate the copolymer begins to decompose at 321℃.The fabricated white LED owes color rendering index up to 91 and corrected color temperature of 5967 K.After UV aging test,these performances have no obvious change and the LED fabricated with the copolymer shows luminance loss of 10.4%,indicating that the copolymer has excellent UV resistance.