Preparation And Properties Of Eu²⁺-doped Oxide Based LED Used Luminescence Materials

As a new generation of lighting source,white light-emitting-diodes(WLEDs)have attracted wide attention due to its advantages of energy saving,environmental protection,high efficiency and portability.As one of its key components,the luminescent materials have more or less deficiencies in luminescence efficiency,excitation spectrum matching,thermal stability and synthesis conditions.In addition,with the continuous development of near infrared analysis and detection technology,the lack of near infrared luminescent materials with high-performance has restricted the progress of this technology.Trying to solve the above problems,this paper selected Eu²⁺with f-d transition as the activator ions and oxide materials as the hosts to develop and explore several new blue,cyan,yellow and near infrared luminescent materials.On the one hand,the relationship between phase,structure and properties is explored to enrich the luminescence mechanism.On the other hand,their application value is also researched and thus provide the ideas for the development of oxide luminescent materials.The main contents and results are as follows:1.A blue luminescent material SrHfSi₂O₇:Eu²⁺was designed and synthesized by high temperature solid-state method.The crystal structure,microstructure and luminescent properties were determined by XRD Rietveld refinement,TEM,X-ray energy spectrum,photoluminescence and cathodeluminescence.Under near-ultraviolet(n-UV)light excitation,the material can emit bright blue light peaked at456 nm,and the internal quantum efficiency is 52.95%.At the same time,under consecutive electron bombardment,the sample shows blue emission with excellent degradation property;2.A cyan luminescent material RbBa₂(PO₃)₅:Eu²⁺(RBP:Eu²⁺)was prepared by high temperature solid-state method at 700 ?.Under the excitation of n-UV light,the emission spectrum of the sample presents an asymmetric cyan emission,with a full width at half maximum of 166 nm.The emission peak of RBP:Eu²⁺can be fitted into two single peaks.The test of time-resolved photoluminescence spectra and structure analysis indicate that Eu²⁺selectively enter the Ba1 and Ba2 sites.Due to its excellent structural rigidity,the thermal stability of the sample is better than that of commercial BaMgAl₁₀O₁₇:Eu²⁺and(Sr,Ba)₂SiO₄:Eu²⁺;3.Two kinds of phosphate luminescent materials Sr₈CaBi(PO₄)₇:Eu²⁺(SCBP:Eu²⁺)and Rb₂SrP₂O₇:Eu²⁺(RSP:Eu²⁺)were successfully obtained by high temperature solid-state method.There are five different Sr/Ca sites in SCBP structure.When Eu²⁺ions enter the lattice,it can exhibit a wide band yellow emission peaked at606 nm under 400 nm light excitation.The thermal stability of SCBP:Eu²⁺is not good,the main reason is that the cationic polyhedra are mostly connected in the way of edge-sharing or corner-sharing,which affects the rigidity of the structure;at the same time,its activation energy is low and the non-radiative transition is prone to generated which will loss energy in the process of heating up.Besides,the yellow luminescent material RSP:Eu²⁺was synthesized at 850 ?.The material can respond to the radiation of n-UV light effectively and emit bright yellow light,the internal quantum efficiency is up to 72.96%,and the color purity is 87.1%.In order to optimize and adjust its luminescent properties,RSP:0.5%Eu²⁺,yCa²⁺(0?y?1)solid solution is designed and obtained.With the increase of Ca²⁺substitution,the emission peak can shift from 575 nm to 613 nm,which can be explained by the increase of crystal field splitting and Stokes shifts.In addition,using RSP:0.5%Eu²⁺and BAM:Eu²⁺as binary complementary phosphors,a white LED lamp was obtained;4.For meeting the demand of high quality NIR luminescent materials,K₃ScSi₂O₇(KSSO),a silicate material with compact structure and multiple cationic lattice,was selected as the host,and Eu²⁺was used as the activator.A NIR luminescent material KSSO:Eu²⁺with wide emission band was obtained by high temperature solid-state method.It can absorb n-UV light and blue light effectively.The emission peak located at 735 nm with a full width at half maximum of 170 nm.KSSO:Eu²⁺showed excellent thermal stability,and the PL intensity at 150 ? was still 70.4%of the initial value.A NIR pc-LED device was fabricated by using a 450 nm LED chip and KSSO:Eu²⁺sample.The NIR output power and photoelectric conversion efficiency are 6.103m W and 23.549%@100m A,respectively.