Research On The Particle Size Dependent Quantum Efficiency Of M₂Si₅N₈:Eu²⁺ Phosphors

Mini-LED has many advantages such as energy-saving,high brightness,and ultra-high contrast.However,the poor luminescence ability of red min-LED chips limits their full-color application.The color conversion materials converted laser lighting technology has the characteristics of energy-saving,compactness,and high power,and is recognized as the next generation of high-brightness and high-power lighting technology.However,the lack of high-quality fluorescent conversion materials for red lasers restricts its application.The preparation of red phosphor with small particle size,high quantum efficiency,and high stability is the key to promoting the industrial application of Mini-LED and laser lighting technology.Therefore,in this work,a simple process combined with ball milling,centrifugation,and pickling of commercial M₂Si₅N₈:Eu²⁺phosphors was used to successfully prepare fine-grained red phosphors with high quality.The mechanism of the quantum efficiency of the phosphors varying with particle size was proposed,and a red Mini-LED device and red fluorescent ceramics with excellent optical properties were constructed.The specific results are as follows:Preparation of M₂Si₅N₈:Eu²⁺red phosphor with small particle size.Two M₂Si₅N₈:Eu²⁺red phosphors Sr₂Si₅N₈:Eu²⁺and Sr Ba Si₅N₈:Eu²⁺red phosphors with different particle size distribution were prepared by ball milling combined with centrifugation and pickling.The median particle size of the quantum efficiency reduction is～3μm,and the two phosphors show the same quantum efficiency of 75%and 80%as the original powder.Continue to reduce the particle size of the phosphor,the silicon dangling bonds on the surface of the phosphor increase,and the quantum efficiency drops significantly.The thermal quenching property of Sr Ba Si₅N₈:Eu²⁺remained>90%@473 K,and the thermal cracking phenomenon did not occur in all particle size distributions（temperature increased to 598 K and reduced to room temperature,air）.Red mini-LED and fluorescent ceramic construction.The small size Sr Ba Si₅N₈:Eu²⁺phosphor was encapsulated on a blue mini-LED chip(λ_em=450 nm,100×200μm²)to obtain bright red light.When the input current is 60 m A,the luminescence saturation is up to 34.3 Mnits,and the ultra-high external quantum efficiency of more than 31%is displayed when driven by a small current of less than 1 m A.In addition,the small particle size Sr Ba Si₅N₈:Eu²⁺phosphor was prepared by ion discharge sintering（SPS）,and the single-phase red fluorescent ceramics with bright luminescence were obtained.The internal quantum efficiency of the obtained fluorescent ceramics is 98.5%（78.8%）of the original powder,and the conversion efficiency of 78.8 lm/W is displayed in the reflection mode.In summary,this paper successfully prepared high-quality red M₂Si₅N₈:Eu²⁺phosphor with small particle size using a set of simple technical processes,and showed a broad application prospect in the field of fluorescent conversion materials for Mini-LED and laser,accelerating the development process of mini-LED full-color and laser lighting and display light source.