Research On Obtaining Full-spectrum LEDs Based On Powder Sedimentation Packaging Method And Its Luminescence Properties

In recent years,the concept of high-quality and healthy lighting has continued to gain popularity.Based on this,high-quality white LEDs,especially close to natural light(sunlight spectrum),that is,full-spectrum white LEDs have become a research hotspot in the lighting field.In this paper,a large-size,wide-thickness red phosphor Ca Al Si N3:Eu2+ and a small-size high-brightness blue(cyan)phosphor(Sr,Ca,Ba)5(PO4)3Cl:Eu2+ are combined with commercial Y3(Al,Ga)5O12:Ce3+ green powder to obtain the host material,a 400 nm violet LED chip is used as the excitation source,and a series of high-quality full-spectrum white-light LEDs that can simulate the visible part of sunlight are manufactured using the powder subsidence packaging method.The electroluminescence performance of white LEDs and the overall weatherability of the device have been systematically studied.The main findings are as follows:(1)A series of Ca Al Si N3:x Eu2+ phosphors were synthesized by high-temperature solid-phase method.Among them,Ca Al Si N3:0.01Eu2+ showed the best luminous properties.Taking it as the research object,nitrogen pressure and Na F+Sr F2 flux are used to help adjust the crystalline characteristics and morphology of the particles.By adopting the method of high temperature melt recrystallization twice,the sample can be thickened and fired to a large particle size of over 20 ?m.XRD tests showed that all the synthesized Ca Al Si N3 samples were pure phases.Through the sintering process above,the crystallization properties of Ca Al Si N3:0.01Eu2+ can be greatly enhanced,and thus the red light emission intensity can be effectively improvedat 650 nm.Due to the characteristics of Ca Al Si N3:0.01Eu2+ with large particle size and wide thickness,the material has a sedimentation phenomenon when packed full-spectrum white LEDs.(2)A series of(Sr,Ca,Ba)5(PO4)3Cl:Eu2+ blue(cyan)phosphors were synthesized by placing the raw materials in an environment where the reducibility is NH3<CO<N2-H2<H2 in order by high temperature solid phase method.The effect of different sintering atmospheres on the performance of Sr5(PO4)3Cl:y Eu2+ series phosphors was investigated.The results showed that in a weakly reduced(NH3)environment,high brightness Sr5(PO4)3Cl:0.05Eu2+ blue phosphor can be obtained.By adding Ca Cl2 flux to control the morphology,spherical particles with small particle size were obtained,with an average particle size of about 7.60 ?m.Adding the matrix cations Ca2+ and Ba2+ can change the crystal field environment of Eu2+,so that the emission peak of the product can be shifted from 455.1 nm to 493.6 nm,thereby obtaining a phosphor with adjustable color from blue to cyan.Due to the small particle size of(Sr,Ca,Ba)5(PO4)3Cl:0.05Eu2+,when this phosphor was used as the blue(cyan)component in full-spectrum white LEDs,there will be no sedimentation during packaging.(3)Based on the violet chip + three-primary phosphors to achieve white LEDs,a 400 nm LED chip with self-made Ca Al Si N3:Eu2+,(Sr,Ca,Ba)5(PO4)3Cl:Eu2+ and commercial Y3(Al,Ga)5O12:Ce3+ green powder combination,a series of full-spectrum white light LEDs with variable color temperature are manufactured by powder sedimentation packaging process.Based on this idea of powder sedimentation packaging,Ca Al Si N3:0.01Eu2+(D50 = 20.37 ?m)red powder with large particle size during the above packaging process will settle.After the sedimentation,a layered structure with red powder sinking down and blue powder floating up which avoid that the red powder absorpt the light from blue powder.Therefore,the color rendering index and luminous efficiency of white LEDs are effectively improved.The color rendering index of each device is over 97,and the highest is 99.3.During the packaging process,the full spectrum(2700,3000,4000,5000,6000,6500 K)LEDs with different color temperatures can be obtained by changing the proportion of phosphors of various colors.In order to further evaluate the applicability of the device as a high-quality lighting source,the weather resistance of the device was tested.The results showed that the device exhibited extremely high stability in harsh environments,indicating that the manufactured white light device is reliable and durable.Therefore,high-quality full-spectrum white-light LEDs illumination that can simulate the visible light spectrum of sunlight is realized.