Study On The Synthesis And Luminescence Properties Of Pyro-silicate Blue/cyan Phosphors For Full-spectrum White LED

White LED(light-emitting diodes,referred to as"light-emitting diodes")have become the mainstream of current white light illumination due to their high luminous efficiency,low power consumption,long life,high reliability,and environmental friendliness.One of the ways to realize white LED is to package the red,green and blue phosphors on the UV chip.However,compared with the full spectrum of sunlight,the spectrum obtained by this method has an obvious"gap"in the cyan region,which makes the spectral integrity and continuity worse.In addition,most Eu²⁺-activated blue-emitting phosphors generally have low absorption efficiency in the near-ultraviolet(n-UV)region and lack short-wavelength blue light emission(<450 nm),resulting in UV light leakage or poor color rendering.Therefore,the development of short-wavelength blue-emitting phosphor with high absorption efficiency and cyan-emitting phosphor with excellent performance is of great significance for realizing full-spectrum healthy lighting.In this paper,Eu²⁺-doped pyrosilicate was used as the research object,and a short-wavelength blue-emitting phosphor NaSrScSi₂O₇:Eu²⁺with high absorption and the cyan-emitting phosphor NaBaLuSi₂O₇:Eu²⁺with good thermal stability were successfully synthesized by high temperature solid-phase reaction method.The luminescence properties and thermal stability were studied in detail.The main research contents and results are as follows:(1)A novel short-wavelength blue-emitting phosphor NaSrScSi₂O₇:Eu²⁺was successfully prepared.Its crystal structure,luminescence properties,fluorescence decay curve,quantum efficiency and thermal stability were studied in detail.Under the excitation of 345 nm,the NaSrScSi₂O₇:0.03Eu²⁺phosphor exhibits an asymmetric emission spectrum centered at 427nm and has a high absorption efficiency of 84.35%.The blue-emitting phosphor and commercial phosphors were encapsulated to obtain WLEDs devices with a low correlated color temperature(CCT)of 3726 K at a driving current of 80 mA.Compared with WLEDs without the as-prepared blue-emitting phosphor,the spectrum effectively compensates for the short-wavelength part,and the special color rendering index R₆ and R₇ increase from 95.2 and 94.5to 98.3 and 96.5,respectively.These results indicate that NaSrScSi₂O₇:Eu²⁺is a promising blue-emitting phosphor candidate for full-spectrum lighting.(2)Based on the above research system,a cyan-emitting phosphor NaBaLuSi₂O₇:Eu²⁺was successfully prepared by the cation replacement method.The crystal structure,luminescence properties and thermal stability of the phosphor were systematically studied.When the excitation light wavelength is 365 nm,the NaBaLuSi₂O₇:Eu²⁺phosphor exhibits an asymmetric emission spectrum with the emission center located around 479 nm.The sample NaBaLuSi₂O₇:0.01Eu²⁺shows good thermal stability,and the luminescence intensity at 423 K can still maintain about 70%of the initial value at 298 K.Finally,WLEDs devices were obtained using 365 nm chips,commercial red/green/blue phosphors,and the prepared cyan-emitting phosphor encapsulation.At a driving current of 100 mA,the WLEDs with cyan-emitting phosphor emits warm white light.Compared with the WLEDs without cyan-emitting phosphor,the correlated color temperature decreases from 3934 K to 3731 K,and the Ra value increases from 86.3 to 96,the R₁₂ increased from 69 to 89,which effectively improved the color rendering index of the device.The results show that NaBaLuSi₂O₇:Eu²⁺has application prospect in improving the quality of full-spectrum lighting.