可用于近紫外LED芯片的铕-铱双金属配合物红光共聚荧光粉.pdf

文章编号2097-1842（2024）02-0468-13A red-emitting copolymer phosphors based on bimetallicEu-Ir complex for Near-UV chip-based LEDsWANGZi-hao1，YANGYa-min1，ZHANGAi-qin2，JIAHu-sheng1，JIAJing3*（1.College of Materials and Science and Engineering,Taiyuan University ofTechnology,Taiyuan 030024,China；2.College of Textile Engineering,Taiyuan University of Technology,Taiyuan 030006,China；3.College of Aeronautics and Astronautics,Taiyuan University of Technology,Taiyuan 030006,China）*Corresponding author，E-mail:Abstract:Inthispaper,anewEu-IrbimetalliccomplexEu(FIrPic)2(Phen)UAissynthesizedusingtheIrcomplexFIrPicasligandsforEuionsandred-emittingphosphorescentcopolymerPM-Eu-IrissuccessfullypreparedviaradicalpolymerizationforcommercialnearUVchip-basedLEDs.TheEu3+ionswerefoundtobeeffectivelysensitizablebyaddingIr-complexwithenhancedultra-violetlightabsorptionataround400nmwithoutaffectingthefluorescenceemissioncharacteristicoftheEu3+ions.TheproposedcopolymerPM-Eu-Irexhibitsthestrongestemissionpeakat612nmwiththeCIEcoordinates(0.461,0.254)under365nmultra-violetlightexcitation,whichmatcheswellwiththe365nmnear-UVchip.Themicro-morphologyoftheredcopolymerphosphorPM-Eu-Irisatypicalmultilayerspatialnetworkstructure;aswellashavingappreciableredemissionandthecorrespondingfluorescencelifetimeof634.54s,italsohasexcellentthermalstabilityinawiderangeof25250C.TheLEDsfabricatedbythecopolymerPM-Eu-Irdisplayredlightemissionwitha149800cd/m2luminance.Theresultssupportthepotentialutilizationofpreparedcopolymerphos-phorasaredcomponentinthefabricationofnearUVchip-basedwhiteLEDs.Key words:rare-earthluminescentions;bimetalliccomplexes;copolymerphosphors;NUVLEDchips收稿日期：2023-09-02；修订日期：2023-10-07基金项目：国家自然科学基金（No.21972103）；山西浙江大学新材料与化工研究院研发项目（No.2021SX-AT010）Supported by National Natural Science Foundation of China(No.21972103);Research and DevelopmentProjectofNewMaterialsandChemicalEngineeringResearchInstituteofShanxiZhejiangUniversity(No.2021SX-AT010)第17卷第2期中国光学（中英文）Vol.17No.22024 年 3 月ChineseOpticsMar.2024可用于近紫外 LED 芯片的铕-铱双金属配合物红光共聚荧光粉王子豪1，杨亚敏1，张爱琴2，贾虎生1，贾静3*（1.太原理工大学材料与科学与工程学院,太原030024；2.太原理工大学轻纺工程学院,太原030006；3.太原理工大学航空航天学院,太原030006）摘要：本研究以 Ir 配合物 FIrPic 作为 Eu 离子的配体，合成了一种新的 Eu-Ir 双金属配合物 Eu(FIrPic)2(Phen)UA，并通过自由基聚合成功制备了红色发光荧光共聚物 PM-Eu-Ir，适用于商用近紫外芯片型 LED。在不影响Eu3+离子的荧光发射特性的前提下，加入Ir-配合物可以有效地敏化Eu3+离子，增强其对400nm 紫外光的吸收。在365nm紫外光激发下，共聚物PM-Eu-Ir在612nm处显示出最强的发射峰，其CIE坐标为（0.461，0.254），这与365nm近紫外芯片非常吻合。红色共聚荧光粉PM-Eu-Ir的微观形貌为典型的多层空间网络结构，除了表现出明显的红光发射和634.54s的荧光寿命外，还在25250C的宽温范围内具有优异的热稳定性。使用共聚物PM-Eu-Ir制作的LED发出的红光亮度为149800cd/m2。研究结果表明，所制备的共聚荧光粉可作为红光元件用于制造近紫外芯片白光LED。关 键 词：稀土发光离子；双金属配合物；共聚型高分子荧光粉；近紫外 LED中图分类号：TQ422文献标志码：Adoi：10.37188/CO.EN-2023-00231IntroductionWhiteLEDsareknownasthefourthgenera-tionoflightsourcesafterincandescentbulbs,fluor-escent,andhigh-pressuregasdischargelamps.Theyofferhigh luminous efficiency,low energy con-sumption,long service life,low weight,environ-mental friendliness,and anti-vibration advanta-ges1-3.White LEDs are achieved mainly throughlight-convertingtechniques,whicharelow-costandeasytorealizeindustrially.OnecurrentproductiontechnologyistoexcitetheyellowphosphorusinganLEDbluechipsuchthatthetwomixedradiationsgeneratewhitelight4-6.However,thescarcityofredemission in the visible spectrum of artificial lightleadstothewhiteLEDdeviceslowcolorrenderingindex7.Furthermore,human eyes are especiallysensitive to blue light,with excessive blue lightstimulationcausingvisualfatigueanddisordersofthe circadian rhythm8.To overcome the abovedrawbacks and improve the light color stability,JungHanet al.9proposedanalternativesolutionfor manufacturing white light in September 1998,namelythe“ultravioletchip+red/green/bluetricol-or phosphors”mode.In this mode,the luminousperformanceofwhitelightdependsstronglyontheratiosofthreeprimarycolorphosphors.Atthesametime,redemissionplaysaroleinadjustingthecol-ortemperatureandcolorrenderingindex.Near-ul-traviolet(N-UV)chip-basedwhite LEDs have re-ceivedconsiderable attention regarding many ap-plications,such as operating theatres,museums,healthlighting,andplant-growthlighting,becauseoftheir more optimal color stability and fluores-cence,aswellastheirbetteruserexperienceandeyefriendliness10-12.Redlightisvitalindeterminingthecolortem-peratureandcolorrenderingperformanceofwhiteLEDdevices.Thus,new red phosphors have be-come one of the research hotspots in the whiteLEDsindustry.ManyscholarshavedevelopedEu3+andTb3+dopedinorganicphosphors,whichexhibitexcellent luminous properties13-16.Numerous re-第2期WANGZi-hao,et al.:Ared-emittingcopolymerphosphorsbasedonbimetallic.469searchers are committed to introducing rare earthcomplexesintopolymermatrixcompositesinordertoobtainrare-earth-dopedpolymerphosphorswithhighluminousefficiencybecauserareearthionsex-hibitexcellentluminescenceproperties17,andpoly-mermaterials have significant advantages in ma-chine-shaping,for example,lightweight,and low-cost18-19.Atpresent,Eu3+ionisoftenusedasared-lightactivatorbecauseofthe5D0/7FJtransitions(J=04)ofEu3+ionthatleadstoacharacteristicredemission band around 610nm20-22.For example,ChangCHet al.23designedandsynthesizedthecomplexes Eu(pzc)3(phen)and Eu(mpzc)3(phen)with an excitation band between 250and 350nm,themostintenseemissionbandbeinganarrowpeakcenteredat614nm.MatsushitaAFYet al.24pre-paredaredlight-emittingmacromolecularcompos-ite Eu(PSA)Phen,which produced an excitationbandbetween275nmand375nmandamainemis-sionbandof610630nm(redemission)whenex-citedat348nm.Thesteady-stateexcitationandemissionspec-traforred-emittingeuropium(Eu)complexestendtobenarrow-bandspectrawithweakemissionin-tensities.Their characteristic absorption peaksmainlyconcentratearound340nm,andtheyexhib-itweakabsorptionofvioletlightat400nm,whichdoesnotmatchwellwiththeoutputwavelengthofcommercialN-UVLEDchips(350420nm)25-26.Incontrast,the excitation spectrum of iridium(Ir)complexeshasabroadbandstructure,whichcanbeeffectivelyexcited by UV and blue light,corres-pondingtoawidecoverageoftheemissionspec-trum.BysynthesizingspeciallydesignedligandsforIrcomplexesandmodulatingthecoordinationpat-tern,broadbandemissionspectracanbeobtainedinanyrangefromtheN-UVtotheN-IRregion,thusenablingsensitizationoflanthanideions27,includ-ingEuions.This paper proposes a simple and practicalsolutiontoachievebroadbandexcitationofEu(III)ion-dopedpolymerphosphorsandbroadentheap-plicationscopeofredfluorescentpolymericmateri-als.TheproposedmethodinvolvessynthesizingtheEu-IrbimetalliccomplexusingIrcomplexesastheligandforEuions,thenpreparingaredcopolymerphosphor through free-radical polymerization.Thepaper then evaluates the materials optical andthermalpropertiesforpotentialapplicationinN-UVLEDs.2Experiments2.1MaterialsEuropium chloride(EuCl3,99.99%),1,10-phenanthroline(Phen,99%),bis2-(4,6-difluoro-phenyl)pyridinato-C2,N(picolinato)iridium(III)(FIrPic99%,Luminescence Technology Corp.),andundecylenicacid(UA,99%),ethanol99.7%,methanol 99.5%,methyl-methacrylate(MMA99%),dimethylsulfoxide(DMSO,AR),azodiisobu-tyronitrile(AIBN98%).2.2Experiments2.2.1SynthesisofbimetalliccomplexEu(FIrPic)2(Phen)UA1mmol EuCl3,2mmol FIrPic,1mmol Phen,and 1mmol UA,according to the substance con-tentof1211,wereseparatelydissolvedin5mLanhydrous ethanol for use.The UA ethanol solu-tion was then injected into a 100mL three-neckflask and stirred for about 10minutes at 50 C.Subsequently,the EuCl3 ethanol solution wasaddeddropbydroptothemix,whichwasneutral-izedtopH4.5with1mol/LNaOHethanolsolution.Afterfurtherstirringfor30minutesat50C,theFIrPic ethanol solution was added to the blend,and a large amount of white precipitate becamevisible during the neutralization of the blendedsolution to pH 7with 1mol/L NaOH ethanolsolution.Finally,the Phen ethanol solution wasadded to the reaction mixture via a dropper andthenstirredforthreemorehoursat50C.Atthe470中国光学（中英文）第17卷endoftheexperiment,theprecipitatewaswashedseveral times with ethanol and dried in an ovenat55Cuntilaconstantweightwasreached.Thewhite powder resulting from this process wasEu(FIrPic)2(Phen)UA.The synthesis route of theproposed Eu-Ir bimetallic complex is shown inFigure1.EuCl32+FFF+H2C=CH(CH2)8COOHH2CCH(H2C)8COOEuNN2OOIrNNNFFFCH2CH3OH(502)F+3NaOH+3NaCl+3H2O+NNFNNIrNOOFig.1Synthetic route of the bimetallic complex Eu(FIr-Pic)2(Phen)UA2.2.2SynthesisofcopolymerphosphorPM-Eu-IrThe reactive complex Eu(FIrPic)2(Phen)UA(0.05g)andMMA(1.28g)werecompletelydis-solvedintheDMSOsolution(10mL)usinganul-trasonicbath.Theresultingmixturewasthenpouredintoa100mLthree-neckflask,wherethereactionwascarriedoutunderanitrogenatmosphere.Sub-sequently,2mL of AIBN ethanol solution(pureAIBNis0.04g)wasaddeddropwisetothemixingsolutionsplacedinthewaterbathat(782)C,anddeoxygenationbynitrogengasstoppedwhenthere-activesystembecameveryviscous.Afterthat,theclosedsystemremainedat78Cfor48hourstoen-sureacompletereaction,andallreactantswereim-mersed in 100mL methanol at room temperature.After two hours,the white flocculent precipitatestartedtogenerate.Finally,thecollectedprecipitatewas filtered through three-layer filter paper andwashedwithDMSOsolutionthreetimestoremoveunreactedmonomersandimpurities.Then,theres-ultingproductsweredriedinanovenat60Cfor48hoursuntilaconstantweightwasreached.Aftergrindingthesubstancethoroughly,awhitepowdercalledpoly(MAA-co-Eu(FIrPic)2(Phen)UA),abbre-viatedasPM-Eu-Ir,wasobtained.Figure2showsthespecificsynthesisroute.xFFFH2CCHFNNIrNOO(H2C)8(CH2)8COOFEu2OOIrNNNFDMSO/AIBN(782)FFNNCOOEuN+y H2CCCCH3CH3CH3CCH2CH2HCxCOyOCH3OON2Fig.2SynthesisrouteofthecopolymerPM-Eu-Ir2.3CharacteristicsFT-IR spectra in the 4000500cm1 rangewererecordedinaKBrpelletusingaFouriertrans-form infrared spectrometer(FTIR,Tensor 27,Bruker).TheUV-visabsorptionspectraweretakeninmethylenechloride(CH2Cl2,104mol/L)usingaHitachi-U3900spectrometer.Fluorescence spectraweremeasuredbyafull-functionsteady-statefluor-escencespectrometer(Fluoromax-4,Horiba)withaslitwidthof5nm,andthepreparedphosphorwasdissolvedin104mol/Lmethylenechloride.Ther-mogravimetric Derivative thermogravimetry(TG-DTG)analysis and differential scanning calori-metry(DSC)curvesonphosphorescentcopolymerwereconductedusingathermalanalysisinstrument(209F3,NETZSCH)withaheatingrateof10C/minunderN2.Thefluorescencelifetimeofthephos-phorescent copolymer was measured in the solidstate using a fluorescence spectrometer(FLS980,Edinburgh).The quantum efficiency(QE)wasmeasuredbyanFLS-980fluorescencespectropho-tometerequippedwitha450WXelightsourceinintegrating sphere mode.The morphology of thesyntheticcomplexandpreparedphosphorescentco-polymerwasobservedusingFE-SEM(JSM-6700F,JEOL).The ST-900M photometer and Keithley2400digitalsourcemetermeasuredelectrolumines-cencespectra.Allmeasurementsweremadeatroomtemperatureunlessotherwisestated.3Resultsanddiscussion3.1SolubilityThe bimetallic complex Eu(FIrPic)2(Phen)UA第2期WANGZi-hao,et al.:Ared-emittingcopolymerphosphorsbasedonbimetallic.471synthesizedinthispaperexhibitsgoodsolubilityinsomehighlyandmoderatelypolarsolvents,suchasDMSO,DMF,CH2Cl2,CHCl3,andTHF,butpoorsolubilityinwater,methanol,andacetone.Further-more,because of the linear macromolecule struc-tureofthepreparedPM-Eu-Ir,theredphosphores-centcopolymerhasexcellentsolubilityinmostpo-lar solvents containing acetone,THF,CH2Cl2,CHCl3,DMSO,and DMF at room temperature,whichsignificantlyimprovesthefilm-formingper-formanceoforganicphosphors.3.2FT-IRspectraThe FT-IR spectra of the Ir complex FIrPic,syntheticEu(FIrPic)2(Phen)UA,andcopolymerPM-Eu-IrrecordedbyKBrtabletsintherange4000400cm1aregiveninFigure3(coloronline).Thecorrespondingcharacteristicpeaksthereofareillus-tratedinTable1.InFigure3(a),FIrPicasthefirstligandshowstwoC-Cstretchingvibrationsofthearomaticringat1346and1292cm1andtheC-Fstretchingvibrationat1246cm1.Besides,theC=NstretchingvibrationofFIrPicoccursat1477cm1,and two C-N stretching vibrations are found at1165 and 1107cm1.In addition,the absorptionband at 1051cm1 is ascribed to the in-plane CHbendingvibrationofthearomaticring,andtheab-sorptionbandsat833,762and700cm1areattrib-utedtotheout-of-planeCHbendingvibrationsinthe900670cm1region.4 000(a)3 7383 3931 6471 6011 5631 4771 4061 3461 2461 1651 0518337627005817107851 0531 1401 1861 2421 3041 4141 5041 5431 6122 8602 9302 9743 4261 1071 2921 512Transmittance/(a.u.)3 500Eu(FIrPic)2(Phen)UAFIrPic3 000Wave number/cm11 5001 0005003 500(b)3 4262 9742 9302 8601 5431 5041 4141 3041 2421 1861 1401 0537857105811 6127548439861 0671 1481 1941 2481 3911 4471 4771 6181 7322 9533 0013 439Transmittance/(a.u.)3 000Wave number/cm11 5001 000500PM-Eu-IrEu(FIrPic)2PhenUAFig.3FT-IRspectraoftheFIrPic,Eu(FIrPic)2(Phen)UA,andPM-Eu-IrTab.1 FT-IR characteristic peaks of the ligands,complex Eu(FIrPic)2(Phen)UAComplexvC=O(-COOH)as(CH2)s(CH2)C-OHC-HEu-NC=NFIrPic1647,1406-833,762,700-1477Phen-864,739-1493UA171129252855910-Eu(FIrPic)2(Phen)UA-29302860-785,7105811414COSince the C=O and C-O in carboxyl ion(-COO-)aretwoessentiallyequivalentbondsandarestronglycoupledtoeachother,thecorres-ponding absorption band of the-COO-group inFIrPic is split into two parts:the asymmetricalstretching vibration as(COO)at 1647cm1 andthe symmetrical stretching vibration s(COO)at1406cm1.The(ass)(COO)of241cm1islar-gerthan200cm128becauseFIrPicisamono-co-ordinatecomplex.However,thebimodalcharacter-isticabsorptionbandsarealmostinvisiblewhenthecoupling between two CO bonds in carboxylate(-COO-)isweak.Thissuggestssuccessfulcoordina-tionbetweenthefirstligandFIrPicandEu()ions.Theoverallvibrationmodeofthearomaticringskeleton in the chosen complex FIrPic presents a472中国光学（中英文）第17卷seriesofsharpabsorptionpeaksat1601,1563,and1512cm1 with different intensities.According tothe hard/soft acid/base principle29,the rare-earthEu ion is a classic hard acid with a coordinationnumberof8,whichmakesiteasiertoformstablecomplexeswithhard-baseligandscontainingoxy-gen or nitrogen atoms.Therefore,compared withtheoriginalcomplexFIrPic,thevibrationbandsofthe aromatic ring skeleton of the bimetallic Eu-Ircomplexshifttolowerfrequencies(1612,1543,and1504cm1)asthedegreeofconjugationincreases.Theabsorptionbandat1053cm1iscausedbythein-planeCHbendingvibrationofthearomaticringintheEu-Ircomplex.Compared with the second ligand Phen,theout-of-plane C-H bending vibrations of the aro-matic ring of the Eu-Ir complex are shifted from864and 739cm1 to 785and 710cm1,respecti-vely.The-C=N stretching vibration shifts from1493cm1to1414cm1becausetwoEu-Ncoordin-ation bonds formed in the coordination of theEu(III)ionwiththesecondligand,Phen,resultinginareducedforceconstantofC=N30.Hence,thecor-respondingabsorptionpeakshiftstolowerfrequen-cies,indicating that the coordination between thesecondligandPhenandEu()ionsissuccessful.The absorption peaks at 2925and 2855cm1arerelatedtotheasymmetricCH2stretchingvibra-tionandsymmetricCH2stretchingvibrationintheactiveligandUA,respectively.WhenEu(III)ionsform a stable complex with UA,the relevantvibrationpeaks will shift towards higher frequen-cies because of the hyperconjugation effect;forexample,the asymmetrical stretching vibrationas(CH2)and symmetrical stretching vibrations(CH2)of Eu(FIrPic)2(Phen)UA are shifted to2930and2860cm1.The ab