Optical Properties Of Blue And Cyan Phosphors For Near-Ultraviolet Excited Full-Spectrum White LED

In order to improve the light and color quality of white LED devices and meet the requirements of healthy lighting,the lighting field proposes the concept of simulated sunlight spectrum-full spectrum LED lighting technology.Full spectral white LED devices can be obtained by excitation of blue(or wide/-band cyan),green and red phosphor using a near-ultraviolet chip.However,the current blue and cyan phosphors excited by near-ultraviolet chips generally suffer from low quantum efficiency and poor thermal stability.Therefore,this thesis investigates the improvement of luminescence intensity and thermal stability of blue phosphor Sr₅(PO₄)₃Cl:Eu²⁺and cyan phosphor(Sr,Ba)₅(PO₄)₃Cl:Eu²⁺by cation substitution method.Developed blue phosphors Na Ba₃Si₂O₇F:Ce³⁺and Na Ba₃Si₂O₇F:Eu²⁺that can be efficiently excited by near-ultraviolet light,and studied and improved their luminescent properties.The contents and results of the study are as follows:(1)phosphors Sr_5-xRE_x(PO₄)₃Cl:Eu²⁺(RE=La,Gd and Lu)and phosphors(Sr,Ba)_5-xRE_x(PO₄)₃Cl:Eu²⁺(RE=La,Gd and Lu)were synthesized by high temperature solid-phase method Y,La,Gd,and Lu).It is found that the luminescence intensity and thermal stability of Sr₅(PO₄)₃Cl:Eu²⁺and(Sr,Ba)₅(PO₄)₃Cl:Eu²⁺phosphors can be improved by replacing Sr²⁺with RE³⁺ions.The luminescence intensity of the samples doped with Lu³⁺ions in the Sr₅(PO₄)₃Cl:Eu²⁺phosphor system increased by 1.97 times,and the thermal stability of the samples at 150?increased from 62%to 95%.In the(Sr,Ba)₅(PO₄)₃Cl:Eu²⁺phosphor system,the luminescence intensity of the samples doped with La³⁺ions can be increased by 2.2 times,and the luminescence intensity of the samples doped with Y³⁺ions at 150?can maintain 97%of the initial value.The full spectral white LED was encapsulated with cyan phosphor Sr_3.3Ba_1.5Y_0.2(PO₄)₃Cl:Eu²⁺,the color rendering index of the device Ra=95.5,the correlated color temperature CCT=3047 K,and the luminous efficiency at 60 m A current reaches 96.37lm/W,which meets the requirements of high color rendering index and low correlated color temperature of warm white LED devices.(2)The phosphors of Na Ba₃Si₂O₇F:Ce³⁺/Eu²⁺were synthesized by high temperature solid-phase method.Under near-ultraviolet excitation,the emission of Ce³⁺is at 435 nm and that of Eu²⁺is at 450 nm.The research and analysis of the occupation of Ce³⁺and Eu²⁺in Na Ba3Si2O7F.Since both Ce³⁺and Eu²⁺have non-equivalent charge substitutions in Na Ba₃Si₂O₇F,Si₃N₄ is doped as a charge balancer.Through charge compensation,the luminescence intensities of Ce³⁺and Eu²⁺were both enhanced,and Na Ba₃Si₂O₇F:Eu²⁺exhibited negative thermal quenching performance in the temperature range of 298-398 K.The blue to cyan emission of Na Ba₃Si₂O₇F:Eu²⁺is achieved by replacing Ba²⁺ions with Ca²⁺or Sr²⁺.Finally,the prepared Na Ba₃Si₂O₇F:Eu²⁺phosphor and the purchased green and red phosphors were used to encapsulate a full-spectrum white LED with a color rendering index of95.3 and an associated color temperature of 4026 K.