High Refractive Index Phosphor-in-glass For White LED Packaging And The Control Of Color Rendering Properties

As the fourth generation environmental lighting resource,white light-emitting diode?LED?has been widely applied in various fields.Now the most common method to obtain white LED is the combination of blue chips and epoxy resin?or silicone?embedded with yellow phosphor.However,due to the low thermal resistance,these polymer binder will age in the high-temperature working environment.Therefore,it is difficult to be applied in the high-power devices.In order to enhance the optical performance and reliability of white LED,phosphor-in-glass?PiG?,which is fabricated by multilayer screen-printing and low-temperature sintering,is proposed.To match the refractive index of yellow phosphor and compensate the red light,we mainly focus on the fabrication of glass matrix,characterization of structure and property of PiG,and optical properties of white LED.The achievements are described as follows:1)To increase molar content of La₂O₃ and WO₃ in the SiO₂-B₂O₃-ZnO system,the refractive index of glass matrix is successfully enhanced.When the molar composition of La2O3 and WO3 is 12 mol%,the glass transition temperature,the coefficient of thermal expansion,and the refractive index of glass matrix is 545?,81×10^-7/?,and 1.82 respectively.The properties of this glass matrix meet the requirement of matching CTE with glass substrate and matching refractive index with yellow phosphor.By adding Eu₂O₃ in the glass matrix,it can be excited by 460 nm and produce red light of 615 nm.2)PiG is fabricated on the glass substrate by multilayer screen-printing and low-temperature sintering.The best transmittance of glass matrix is at the sintering temperature of 600?.At 600?,the glass matrix can melt thoroughly to cover phosphor and the phosphor is not eroded very much to retain their origin properties3)As the content of yellow phosphor increases,the intensity of spectra increases first and then decreases.The strongest intensity is obtained when the ratio of glass matrix and yellow phosphor is 6:4.The PiG with Eu₂O₃ or red phosphor can both be excited by the blue light and produce red light.4)The effect of yellow phosphor content,refractive index of glass matrix,and Eu₂O₃/red phosphor on the luminous properties of white LED is investigated.As the content of yellow phosphor increases,the luminous efficacy of white LED increases while the color temperature and color rendering index decrease.When the ratio of glass matrix and yellow phosphor is 5:5,it realizes the output of white light.The luminous efficacy of white LED also increases with enhanced refractive index of glass matrix.Moreover,Eu₂O₃ and red phosphor can improve the color rendering index and color temperature of white LED.The effect of red phosphor is better,while Eu₂O₃ can keep the luminous efficacy.