Design,Preparation And Optical Properties Of WLED Encapsulated With Graded Refractive Index Fluorescent Glass Film

White Light Emitting Diode（WLED）has the characteristics of high electro-optical conversion efficiency,energy saving,environmental protection,long life and compact structure.Known as a new generation of green lighting sources,it is widely used in indoor lighting,automotive lights,background displays and other fields.At present,WLED has the disadvantages of low light output efficiency,poor color quality and poor thermal stability.In order to solve these problems,the motion of photons in phosphor was modeled in this paper using a combination of Monte Carlo simulation and experimental preparation.The effects of the concentration,refractive index,thickness,and packaging method of the phosphor layer on the light extraction efficiency of WLED were determined by these methods.The effects of the concentration,refractive index,thickness,and packaging method of the phosphor layer on the light extraction efficiency of WLED were determined by these methods.The basic parameters were obtained and the regulation of the light-extraction mechanism was analyzed.The specific research contents of this paper are as follows:The first chapter,the working principle,performance characterization method,and research status of WLED are introduced in detail.And the principle and preparation method of refractive index gradient multilayer substrate glass film.The second chapter,in order to explore the effect of graded refractive index fluorescent glass film on the luminous performance of WLED.In this chapter,the refractive index gradient bismuthate fluorescent glass film was prepared using a combination of simulations and experiments.Its effect on the luminous efficiency and color quality of WLEDs was also studied.The effects of phosphor concentration,thickness and coating method on the luminous efficiency of WLEDs were analyzed,the propagation mechanism of photons in the boron bismuthate fluorescent glass film was discussed.And The luminescence performance of the encapsulated WLEDs was tested.The results show that the luminous efficiency of the WLEDs obtained by encapsulating the refractive index gradient bismuthate fluorescent glass film is 89.57%,which is about 30%higher than that of the WLEDs encapsulated with conventional silicone material.The third chapter,in order to improve the color quality and stability of WLED,a graded refractive index Mn⁴⁺-doped lithium silicate fluorescent glass film was prepared in this chapter.A combination of Montecarlo simulation and experimental preparation was utilized to model the photon transport in lithium silicate fluorescent glass films.We investigated the light transmission performance regulation of Mn⁴⁺-doped lithium silicate fluorescent glass film as an encapsulating film,and confirmed the thickness and phosphor concentration of the lithium silicate fluorescent glass film.Performance tests were conducted on the encapsulated WLEDs.The experimental results found that the fluorescent glass film doped with Mn⁴⁺has a higher color rendering index and lower color temperature than the lithium silicate fluorescent glass film.This is because the doping of Mn⁴⁺can effectively supplement the lack of red light component of current WLEDs and improve the color quality and stability of WLEDs.The fourth chapter,in order to confirm the influence of the red light component in the encapsulation material on the WLED luminescence performance.In this chapter,the motion of photons in aluminum fluorosilicate fluorescent glass films was modeled by a combination of montagallo simulation and experimental preparation.Seven kinds of aluminum fluorosilicate fluorescent glass films encapsulating WLEDs were also prepared by experimental operation,and the thickness of the aluminum fluorosilicate fluorescent glass film and the mass ratio of phosphor and glass matrix powder were determined.The experimental results showed that the addition of red phosphor in the encapsulation material can effectively improve the color rendering index and reduce the color temperature of WLEDs.However,with the increase of red phosphor,the light output efficiency of WLED will be slightly reduced.In addition,in the refractive index gradient aluminum fluorosilicate fluorescent glass film,the different distribution positions of red and yellow phosphors will also have different effects on the luminous efficiency of WLEDs.Experiments show that the composite structure of yellow phosphor-yellow phosphor-red phosphor of aluminum fluorosilicate fluorescent glass film can not only effectively improve the color quality of WLED,but also maintain a high luminous efficiency.