Preparation And Luminous Properties Of Phosphor-in-glass With Gradient Refractive Index For White LED Packaging

White light-emitting diode?WLED?has been widely used in transportation displays,signs,and auto-motive lighting for its power efficiency,reliability,lifetime,and lighting quality.However,it is limited to low luminous efficiency,poor color quality and bad thermostability in traditional WLED packages technology.In this work,we introduce telluride zinc phosphor-in-glass?PiG?with gradient refractive index?GRIN?for white LED packaging to enhance luminous efficiency and thermostability.Adding rare earth ions into telluride zinc glass matrix improve its color quality.Specific studies are as follows:1)Preparation and characterization telluride zinc glass matrix.It is found that the well glass formed area was ZnO+Na₂O?25 mol%,Na₂O?25 mol%,B₂O₃?45mol%,at the range of 15-75 mol%?ZnO?40 mol%in TeO₂-ZnO-Na₂O-B₂O₃ glass.TZNB-1^TZNB-7 in this area was used for PiG with GRIN.Properties of TZNB-1^TZNB-7 were investigated.The results demonstrated that when tellurium oxide content was reduced from 75 mol%to 15 mol%,coefficient of thermal expansion?CTE?,glass transformation temperature?Tg?of TZNB-1^TZNB-7 decreased first and then increased,and the refractive index decreased from 2.03 to 1.61.2)The optimal structure of gradient refractive index was determined to be G=4by Monte Carlo simulations and numerical calculations,and which consisted of TZNB-1?n=2.03?,TZNB-4?n=1.79?,TZNB-6?n=1.66?and glass substrate?n=1.52?.PiG with GRIN was prepared by screen printing and low temperature sintering.Sintering temperature,surface morphology,and fluorescence spectra of PiG with GRIN were investigated.The results show that the optimum sintering temperature is575?,and the structure of phosphor crystal was retained completely at this temperature.In addition,the fluorescence spectra show that the structure of gradient refractive index increases the intensity of excitation and emission peaks.3)Luminous efficiency of WLED encapsulants with PiG with GRIN is investigated.The results show that the luminous efficiency of PiG with GRIN?GRIN-1-4-6?enhances 9.51%-23.13%compared with that of traditional structure.Color quality of GRIN and traditional structure were poor.4)Adding rare earth ions into telluride zinc glass matrix.The results show that with Eu₂O₃ increasing,luminous efficiency is reduced,color rendering index is increased and color temperature is decreased.And it is determined that when Eu₂O₃content is 1 mol%,WLED has the best opticl performance.