有机电致发光器件简介

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,有机电致发光器件简介,郝玉英,太原理工大学物理与光电工程系,2009.9.16,2.,1.,有机电致发光研究的背景及应用,有机电致发光器件的结构,3.,器件的发光机理及结构的优化设计,激子的有效利用,-,磷光器件,有机电致白光器件,4.,5.,有机电致发光器件的制备,6.,有机电致发光研究的背景及主要应用,1987,，,C.W.Tang et al.,Alq,3,was used as emitting material and,diamine,derivative as hole transport material.,1963,，,Pope et al.,Anthracene,was used as emitting material,C.W.Tang,有机电致发光的发展历程,1990 J.H.Burroughs et al.,PPV was used as EL material,1998 S.R.,Forrest,et al.,PtOEP,doped in Alq,3,was used as EL material,Stephen R. Forrest,Visible - OLED：,Displays and Lighting,UV- OLED: Optical Sensor and detector,IR- OLED: Optical Communication,有机电致发光器件,(OLED),的主要应用领域,用于显示和照明,OLED,产品,31-inch OLED TV prototype (Samsung,，,2005),有机微显示器件,800 lines/inch,，,30 line/mm;,硅,CMOS,驱动，,4V,工作电压,;,要求顶发射；,工艺难度大，国际上只有两个公司能做彩色微显示器件；,尺寸小,分辨率高,功耗低,可穿戴电脑,头戴式,DVD,影院,液晶上下两层玻璃主要是用来夹住液晶，下层玻璃长有薄膜晶体管,(Thin film transistor, TFT),，而上层玻璃则贴有彩色滤光片,(Color filter),。这两片玻璃在接触液晶的那一面并不是光滑的，而是有锯齿状的沟槽。这个沟槽的主要目的是希望长棒状的液晶分子沿著沟槽排列，如此一来，液晶分子的排列才会整齐。因为如果是光滑的平面，液晶分子的排列便会不整齐，造成光线的散射，形成漏光的现象。但是在实际的制造过程中，并无法将玻璃做成如此的槽状分布，一般会先在玻璃表面涂布一层,PI(polyimide,),，再用布磨擦,(rubbing),，使,PI,的表面分子不再杂散分布，依照固定而均一的方向排列。而这一层,PI,就叫做配向膜,(alignment film),，提供液晶分子呈均匀排列的介面条件，让液晶依照预定的顺序排列。,优点：主动发光、响应快、温度特性好、功耗低、薄型化、宽视角、可弯曲、全色显示、环境友好绿色显示,日本,sony,发明的世界第一款,OLEDTV,只有,3mm,（,2008,年）,OLED vs. LED,OLED: Area Source,Soft Light,LED: Point Source,Bright Light,OLED efficiency,CFL,：,70-90lm/W,LED:50-130lm/W,OLED,已获得大于,100lm/W,的效率，已与无机,LED,相抗衡,有机电致发光光源,面光源,不刺眼,适于室内照明,车内照明,景观照明等,传统,OLED,的结构,Glass Substrate,ITO,EML,Cathode,Glass Substrate,ITO,EML,Cathode,HTL,Glass Substrate,ITO,EML,Cathode,ETL,Glass Substrate,ITO,EML,Cathode,Light out,HTL,ETL,双层结构,三层结构,单层结构,Appl,. phys.,Lett,. 1987, 51:913 ;,Appl,. Phys.,Lett,. 1989, 55(15):1489;,Jpn,. J.,Appl,. Phys. 1988, 27(4):L713,Light out,Light out,Light out,双层结构,HTL,EML,Anode,Cathode,ETL,HIL,EIL,HIL:,空穴注入层,HTL:,空穴传输层,EML:,发光层,ETL:,电子传输层,EIL:,电子注入层,OLED,的多层结构,HTL,EML,Anode,Cathode,ETL,HIL,EIL,Anode,：,透明、导电、高功函数,HIL:,适合的能级、空穴传输、改善界面接触,HTL:,高空穴迁移率、高的玻璃化温度、小空穴注入势垒，大的电子注入势垒,EML:,高发光效率,，,限制载流子在发光层，高的玻璃化温度,ETL:,高电子迁移率，小的电子注入势垒，大的空穴注入势垒，高的玻璃化温度,EIL:,电子注入,Cathode,：,低功函数,OLED,功能层材料要求,Appl,. phys.,Lett,. 1987, 51:913,非掺杂式,OLED,的发光机理,OLED,的发光机理,双注入式复合发光,Electroluminescent mechanism,exciton,cathode,ITO,+,_,electron,hole,OLED,的发光机理,双注入式复合发光,载流子注入,载流子传输,激子的形成,激子的迁移,发光,exciton,: singlet and triplet(1:3),HOMO-LUMO energy gap determines wavelength of emitted radiation.,主客发光体系统,（掺杂器件）的发光机理,1,、,Frster,能量转移（库仑作用力方式）,由,dipole-dipole,作用，距离较长,(50-100),，此种转移方式只能使客体转移成,singlet state,。,电子交换，需要电子云重叠或分子接触，分子间的距离最多只能是几个埃。,须符合,Wigner-Witmer,选择定则,(,交换前后自旋不变，即只发生单重态对单重态和三重态对三重态的能量转移,),2,、,Dexter,能量转移,3,、主客发光体系统的另一发光机制,-,载流子捕陷的方式,当客发光体掺杂在能隙较大的主发光体中，且客发光体的,HOMO,和,LUMO,或其中之一被包含在主发光体的,HOMO/LUMO,能级内，电子和空穴不易注入到主发光体，而容易直接注入到客发光体，在客发光体上复合形成,Frenkel,激子，进而产生客发光体发光。,traps,OLED,结构的优化设计,OLED,的结构设计,-,优化器件性能,设计原则：载流子注入平衡、传输平衡,各功能层,能级匹配,单层结构：,电子与空穴的注入势垒接近，发光材料为双极传输材料，电子迁移率与空穴的迁移率接近,ITO,阴极,OLED,双层结构,阳极,阴极,ETL,EML,阳极,阴极,HTL,EML,发光材料具有电子传输性能，插入空穴传输层，电子在界面处被阻挡并积累，而空穴容易注入发光层，电子和空穴在界面处复合,发光材料具有空穴传输性能，插入电子传输层，空穴在界面处被阻挡并积累，而电子容易注入发光层，电子和空穴在界面处复合,OLED,三层结构,ITO,阴极,HTL,EML,ETL,电子受到空穴传输层的阻挡，空穴受到电子传输层的阻挡，使电子与空穴限制在发光层中，提高电子与空穴复合的几率,HTL,EML,Anode,Cathode,ETL,HIL,EIL,EML,n -ETL,p-HTL,Anode,pin,OLED,结构,Cathode,-,改善电子的注入和传输能力,-,在电子传输层中掺杂活泼金属如,Li,Cs,-,易氧化，扩散,采用氧化物如,Cs,2,O,Al,2,O,3,TiO,2,作为电子注入层,采用碱金属卤化物如,LiF,作为电子注入层,MnO,-,电子注入和传输材料,-,在空气中稳定（绝缘体），避免了活泼掺杂物易氧化的问题,电子的迁移率远小于空穴的迁移率：,1/1000,ITO,阳极,玻璃衬底,空穴传输层,NPB 50nm,电子传输层,Alq,3,:MnO,30nm,发光层,Alq,3,30nm,阴极,Al 150nm,ITO,阳极,玻璃衬底,空穴传输层,NPB 50nm,电子传输层,Alq,3,30nm,发光层,Alq,3,30nm,阴极,Al 150nm,ITO,阳极,玻璃衬底,空穴传输层,NPB 50nm,电子注入层,MnO,3nm,发光层兼电子传输层,Alq,3,60nm,阴极,Al 150nm,ITO,阳极,玻璃衬底,空穴传输层,NPB 50nm,电子注入层,LiF,0.5nm,发光层兼电子传输层,Alq,3,60nm,阴极,Al 150nm,电子传输,电子注入,Appl,. Phys.,Lett,., 2008, 93,：,133301,电流密度，亮度,电子传输,Alq,3,:MnO,器件,Alq,3,器件,电子注入,-,MnO,器件,LiF,器件,器件,Turn-on,voltage (V),at 1 cd/m,2,Maximum,Luminance,(cd/m,2,),Maximum,PE,(lm/W),电子传输,Alq,3,:MnO,3.8,10750,0.7,Alq,3,7.4,6609,0.4,电子注入,MnO,3.1,13710,1.1,LiF,3.4,8452,0.8,功率效率,电子传输, Alq,3,:MnO,器件,Alq,3,器件,电子注入,-,MnO,器件,LiF,器件,微腔,OLED,能有效提高色纯度和效率,Principle of tandem OLED with,p-n,junction CGL,p-doped HTL,n-doped ETL,LUMO,HOMO,E,F,E,F,p-doped HTL,n-doped ETL,p-doped HTL,n-doped ETL,2010,年报道的串联式,OLED,由于有机层的折射率（,1.7-1.85,），玻璃的折射率（,1.49,左右）比空气的折射率大的多，所以发光层产生的光有很大一部分以波导形式限制在这两层中 。根据各层膜折射率的不同可以把发光层产生的光分成如图的四个模式。另外，由于发光层的位置靠近金属阴极，激子能量也会有一部分以非辐射跃迁的形式传递给金属而损耗掉。,根据射线光学计算出只有约,20%,的光耦合到器件外部。,High light out-coupling by,substrate modification,Organic,(n,1,=1.7,1.85,),Al,Electrode,(n,0,=1.0,k=6.5,),ITO(n,2,=2.0,),Substrate,(n,3,=1.5,),(,TF loss, 47%,),(,Sub Loss. 34%,),Out-coupling efficiency, 19%,通过,改变原有光的传播途径,，可以,提高,OLED,器件的光取出效率,。,方法,1,方法,2,激子的有效利用,-,磷光,OLED,激发态的多重性,在激发三重态中，电子和电子之间的排斥作用小于激发单重态的电子，所以激发三重态的能量小。,光致荧光和磷光,Singlet:Triplet,=1:3,Max,（,FL,）,:,Max,（,PL,）,=1:3,singlet life time(10,-9,s 10,-7,s) triplet life time(10,-3,s100s),Hole,injection,Electron,injection,Electron-hole,recombination,Transporting,Exciton,25,S,75,T,Radiation,Ground state,IC,Electrophophorence,EF,(Electro-fluorescence,),and EP,(Electro-,phosphorence,),Electro-fluorescence,100,Radiation,电子,/,空穴 复合形成,singlet and triplet,激子,Experimentally determined singlet fraction for Alq,3,based OLEDs = 22,3% M.A.,Baldo,et.al.,Phys. Rev. B,(1999),Dopant,Emission,Expected singlet fraction based on simple spin statistics =,25%,Energy transfers from host/matrix,excitonic,states to dopant,conserve spin,.,Phosphorescence (triplet emission) is formally,a forbidden process,.,!?!,Dopant traps,exciton and,emits,+,+,and,hole electron,Heavy metal facilitated triplet emission,Strong spin-orbit-coupling mixes singlet and triplet MLCT states, M = Ir, Pt, Os, Re,etc.,MLCT = metal to ligand charge transfer, LC = ligand centered,S,0,ground state,Luminescence,State mixing,1,MLCT,3,MLCT,Ligand centered,triplet,3,LC,400,NPD,200,Ir(ppy),3,in CBP,60,BCP,200,Alq,3,ITO,MgAg,exciton,formation,region,Ir(ppy),3,short lifetime: 500ns in CBP,no fluorescence observed, only phosphorescence,(,f,PL,= 0.4),Iridium, strong intersystem crossing,R.J. Watts,et. al.,Inorg,. Chem,. (1991),M.A.,Baldo,et. al.,Apl,. Phys.,Lett,.,1999,+,Organometallic Ir Phosphor,CBP,BCP,External quantum efficiency of Ir(ppy),3,in CBP,10,-2,10,-1,10,0,10,1,10,2,10,3,0.1,10,External quantum efficiency (%),Current density (mA/cm,2,),6% Ir(ppy),3,in CBP,6% Ir(ppy),3,in CBP,NO,BCP layer,10,-2,10,-1,10,0,10,1,10,2,10,3,0.1,1,10,External quantum efficiency (%),Current density (mA/cm,2,),6% Ir(ppy),3,in CBP,External quantum efficiency of Ir(ppy),3,in CBP,position of dopant HOMO leads to carrier trapping/transport at the dopant, carrier recombination at the dopant increases OLED efficiency,6% Ir(ppy),3,in CBP,NO,BCP layer,-NPD,BCP,Alq,3,ITO,MgAg,IrppyLUMO,Irppy,有机电致白光器件,OLED innovations in light,Device Structure,Emissive layers,Reference,Blue host,doped red guest,Lee, et. al, 2003, Thin Film Solids,Qiu, et. al, 2006, APL.,Red EML/,Blue EML,Forrest, et. al, 1995, APL,Tao, et. al, 2001, APL,Blue EML,/Green EML/Red EML,Kido, et. al, 1995, Science,Forrest, et. al, 2006, Nature,Blue EML,unit/CGL/Red EML unit,Kido, et. al, 2003,SID,Ma, et. al, 2005, APL,Blue EML,/electrode/ Green EML unit /electrode /Red EML,Thompson, et. al, 1997, Science,CCM/,Blue emitting OLED,Foust, et. al, 2002, APL,Zachau, et. al, 2006, APL,CCM,EML,EML,EML,CGL,Approaches to fabricating a high-efficient WOLED,WOLED with three color mix (multi-QW),High efficient device schemes for,Phosphorescent,WOLEDs,ext,=(10.80.3)% 500cd/,p,=(22.10.3)%lm/w,undoped host spacer(4nm),between the blue,fluorophore,and the phosphors prevents direct energy transfer from the blue dopant to the green and red phosphors.,S,eparate energy transfer,S. R. Forrest, et. al., Nature, 2006,High efficient,device schemes,for WOLEDs,Leo, et. al, Nature, 2009,Power efficiency of 90 lmW,-1,at 1000 cd/m2.(potential to be raised to 124 lmW,-1,),An excellent CRI of 80,A brightness of 1000 cdm,-2,slightly above 3 V and 10000 cd m,-2,are reached below 4 V,有机电致发光器件的制备,OLED,的制作,ITO,玻璃清洗,光刻,再清洗,真空热蒸发多层有机层,真空蒸发背电极,真空蒸发保护层,前处理,封装,切割,测试,模块组装,产品检验,老化实验,实验过程,ITO,清洗,UV,处理,真空蒸镀,性能测试,分别用丙酮、去离子水各清洗,15,分钟,清洗两遍,254nm,的紫外灯照射,20,分钟,在真空度,2,10,-4,Pa,下依次蒸镀各层,在大气环境下测量器件的各种性能参数,有机电致发光器件样品,Thanks for your attention！,