阴极耦合层对顶发射白光OLED器件光电性能影响（英文）

为了研究不同厚度C60阴极耦合层对顶发射白光OLED器件光电性能的影响,实验数值计算了半透明阴极组成的多层膜系(ETL/EIL/Mg∶Ag/C60)的透过率;同时,采用共阴极结构设计制备了顶发射白光OLED器件,并对不同厚度的C60折射率匹配层制备的顶发射白光OLED器件的光电特性进行了研究。结果表明,不同C60厚度的多层膜系透过率差异较大,在C60膜层厚度为30～40nm时,多层膜在较宽波段范围内均有高的透过率,且透过率光谱的色坐标最接近白光等能点;通过分析不同阴极耦合层制备的顶部发光OLED器件的光电性能,发现采用适当厚度的C60阴极耦合层材料,可以有效提高器件外量子效率,并在一定程度上能够有效改善器件的色坐标,实现接近等能白光的顶发光OLED器件制备。     

阴极耦合层对顶发射白光OLED器件光电性能的影响

为了分析不同阴极耦合层对顶发射白光OLED器件光电性能的影响,数值计算了半透明阴极组成的多层膜系(ETL/EIL/Mg:Ag/折射率匹配层)的透过率和损耗;同时,采用共阴极结构设计制备了顶发射白光OLED器件,并对不同折射率匹配层制备的顶发射白光OLED器件的光电特性进行了研究。结果表明:采用相同厚度LiF和Al2O3薄膜作为阴极耦合层时,多层膜系光学透过率和损耗曲线存在较大差异;在20mA/cm2电流密度下,随着观测角度的增大,采用LiF+Al2O3双层折射率匹配层制备的器件电致发光谱峰位发生蓝移,但在整个视角内,器件的色坐标均稳定在白光等能点附近,这表明顶发射白光器件的色坐标可以通过折射率匹配层调节,使得器件在较大视角范围均能实现白光发射。     

不同玻璃基板对蓝光OLED的影响

文章使用ADN：TBPe作为荧光金属微腔OLED的发光层,以高反射的Al膜作为阴极顶电极,以半透明的Al膜作为阳极底电极,在不同的玻璃基板上制备了结构为Glass/Al（15nm）/MoO3（60nm）/NPB（40nm）/AND：TBPe（30nm,3%）/Alq3（20nm）/LiF（1nm）/Al（140nm）的荧光金属微腔OLED,研究了在普通玻璃及粗化玻璃的粗糙面和平滑面上蒸镀器件时的光学及电学性能影响。实验结果表明,当蒸镀面为光面时,其器件效率及亮度都优于其它器件。     

利用有机覆盖层提高OLED出光效率

将Alq作为覆盖层真空蒸镀到玻璃基板后制作底发射有机电致发光器件(OLED),所制备的器件结构为:Glass/Alq(xnm)/Al(15nm)/MoO3(30nm)/NPB(60nm)/Alq(65nm)/LiF(1nm)/Al(150nm)。通过研究器件光辐射特性曲线,可以看出覆盖层厚度的变化引起光的干涉效应的变化是导致电致发光变化的原因,广角干涉和多光束干涉之间的相互作用可以通过覆盖层的厚度来调节,并且半透明的Al膜做阳极,将覆盖层蒸镀到阳极之外玻璃基板上,半透明的铝膜和覆盖层与阴极组成微腔器件,通过改变覆盖层的厚度调节微腔的腔长,使OLED电致发光光谱的中心波长发生红移。     

LiF层作为空穴阻挡层的绿色OLED的光电性能研究

采用真空热蒸镀方法,制备了四种Delta掺杂结构OLED器件,其结构为：ITO/m-MTDATA（50nm）/LiF（xnm）/NPB（10nm）/Alq（5nm）/C545T（0.05nm）/Alq（55nm）/LiF（1nm）/Al,都获得了性能稳定的绿色OLED器件。从实验结果分析可知：绿色OLED器件的电流-电压（I-V）特性曲线、亮度-电压（L-V）曲线、亮度-电流（L-I）曲线及效率等光电性能随着LiF厚度的变化而随之改变。从其中总结规律,对OLED器件制作工艺有一定的指导作用。     

光学微腔调节顶发射单色绿光OLED微显示器件色纯度研究

有机电致发光器件的发光颜色与色纯度在很大程度上受限于有机材料本身特性,而通过光学微腔效应可以从器件结构的改变来进行色纯度的调节。本文介绍了一种通过调节有机结构中空穴传输层和电子阻挡层厚度,从而改变器件微腔腔长,获得高纯度顶发射单色发光器件的方法。利用这种方法制作的有机顶发射绿色磷光器件结构为Si Substrate/Ag/ITO/ NPB: F16CuPc(10 nm, 3%)/NPB(x nm)/ TCTA(y nm)/ mCP: Ir(ppy)₃(40 nm, 6%)/ Bphen: Liq(30 nm, 40%)/Mg: Ag(12 nm, 10%)/Alq₃(35 nm),改变NPB和TCTA的厚度,获得了高色纯度发光器件,正向出射绿光的色坐标达到(0.2092,0.7167),接近标准绿光(0.21, 0.71)。     

阴极蒸镀和隔离层对有机发光二极管性能的影响

制备了简单结构的有机发光二极管(OLED)ITO/NPB/Alq3/Al/Ag。实验结果表明,快速蒸镀法制备的Ag阴极越厚,器件性能越差,而慢速蒸镀200nmAg阴极时器件性能也较差。在Alq3与Al阴极之间插入BCP/C60/LiF隔离层后,即使快速蒸镀法制备的Ag厚达280nm,器件的最大电流密度、最大亮度和最大电流效率仍分别高达248.6mA/cm2、5380.7cd/m2和3.52cd/A。隔离层不仅保护NPB和Alq3基本不被玻璃化,还很好地与Alq3和Al阴极匹配,大大提高了器件性能。     

顶发射绿光OLED器件制备及其光电性能研究

实验制备了结构为多层阳极/EHI608/NPB/Alq3:ELL/ETL1/LiF/Mg:Ag/CPL的硅基绿光有机电致发光OLED器件,研究了不同掺杂浓度对器件驱动电压、亮度、发光效率和EL光谱影响.在此基础上,通过在阴极上制备了一定厚度的阴极耦合层CPL,并研究了阴极耦合层对OLED器件微腔效应影响.结果 表明,随着发光层掺杂浓度的增大,器件驱动电压、发光亮度和效率逐渐增加,并出现EL光谱发光峰位红移.同时,随着CPL厚度增加,多层膜系ETL/EIL/Mg:Ag/CPL透过率逐渐增加,当阴极耦合层CPL厚度在30 nm时候,多层膜系结构的透过率和透过频带较高,多层膜系透过率光谱坐标接近白光(0.33,0.33)等能点.此时,顶发射绿光OLED器件在不同视角下EL光谱的蓝移现象最大限度得到了抑制,且EL光谱半峰宽明显增加.     

基于DOPPP的高效白光OLED器件

采用真空热蒸镀的方法,以荧光染料1-(2,5-d imethoxy-4-(1-pyrenyl)-phenyl)pyrene (DOPPP)为蓝发光 层,5,6,11,2-Tetraphenylnaphthacene (Rubrene)为黄发光层,制备了结构为ITO/m-M TDATA(10nm)/NPB(30nm)/ Rubrene (0.2nm)/ DOPPP (x nm)/TAZ(10nm)/Alq₃(30nm)/LiF(0.5nm)/Al的双发光层的高效白色有机电 致发光器件(OLED)。通过调整DOPPP层的厚度,研究器件的发光性能。当DOPPP层厚小 于25nm时,器件以 黄光发射为主;当DOPPP层厚为25nm时器件的性能最佳,在电流密度为209.18mA/cm²时,获得最 大亮度为9232cd/m²,在电流密度为103.712mA/cm²时获得最大电流效率4.68cd/A, 并随着驱动电压 的升高,器件的色坐标从(0.366,0.365)变化到(0.384,0.399),都在白光的范围之内;当DOPPP层厚度超过25nm时,器件的效率和亮度 都开始下降。     

透明叠层结构Ag/MoO_3/Ag阳极对绿光OLED器件性能的影响

本文采用一种结构为Ag/MoO_3/Ag的金属/氧化物/金属(M_1/O/M_2)叠层替代ITO作为OLED器件的阳极,研究Ag/MoO_3/Ag叠层结构变化对于OLED器件电极透过率、亮度、光谱等性能的影响。实验采用真空蒸镀方法制备了一系列器件,器件结构为Ag/MoO_3/Ag/MoO_3(10nm)/NPB(40nm)/Alq_3(60nm)/LiF(1nm)/Al(150nm)。对比器件的电压-电流密度、电压-亮度、光谱特性等数据,表明Ag/MoO_3/Ag的结构为20/20/10(nm)时,器件性能较好。在驱动电压为11V时,其亮度达到18 421cd/m~2,电流效率为2.45cd/A;且因器件中存在微腔效应,其EL光谱蓝移,半高宽变窄。但考虑到530nm处其电极透过率仅为17%,所以经换算该器件实际发光亮度比ITO电极器件更高。该Ag/MoO_3/Ag叠层阳极制作相对简单,经优化后在顶发射和柔性OLED器件方面将具有一定的应用前景。     

覆盖层对顶发射白光微型OLED性能的影响研究

采用两种覆盖层CPL（Capping layer）材料Alq3和ZnSe制备了顶发射白光有机电致发光器件TE-OLEDs（Top emitting white organic light-emitting diodes）,器件结构为ITO/NPB: LiQ (5%) (10 nm) /TCTA(20nm)/FIrpic+3.5%Ir(ppy)3+0.5%Ir(MDQ)2(acac)(25nm)/TPBI(10nm)/LiF(5nm)/Mg: Ag(10%) (12 nm)/CPL。实验结果表明,Alq3和ZnSe作为CPL可以增强TE-OLED器件的出光和调制光谱特性,并且ZnSe作为覆盖层制备的TE-OLED器件色坐标（CIEX,CIEY）随亮度变化更平稳,表现出良好的色稳定性。进一步,通过改变ZnSe厚度来优化器件,当ZnSe为45 nm时,器件获得了最佳的亮度和电流效率,分别为1461 cd/cm2和7.38 cd/A,色坐标为（0.30,0.33）。     

Bphen掺杂Cs_2CO_3作为电子传输层对OLED器件性能的影响

为改善OLED器件的载子注入平衡,本文在其结构ITO/MoO3/NPB/Alq3/Cs2CO3/Al中,分别引入高电子迁移率材料Bphen及Bphen∶Cs2CO3作为电子传输层。通过改变Bphen的厚度以及Bphen中Cs2CO3的体积掺杂浓度,研究其对器件发光亮度、电流密度和效率等性能的影响。实验结果表明,采用Bphen或者Bphen∶Cs2CO3作为电子传输层,均能提高器件的电子注入能力,改善器件的性能。相比于未引入Bphen的器件,采用25nm的Bphen作为电子传输层,改善了器件的电子注入,使器件的最大电流效率提高112%;采用体积掺杂浓度为15%,厚度为5nm的Bphen∶Cs2CO3作为电子传输层,减小了电子注入势垒,使器件的最大电流效率提高27%,并且掺杂层厚度的改变对器件的电子注入影响很小。该方法可用于OLED器件的阴极修饰,对器件性能的提升将起到一定的促进作用。     

Measurement of Electron Mobility in Alq3 From Optical Modulation Measurements in Multilayer Organic Light-Emitting Diodes

The dynamic characteristics of multilayer organic light-emitting diodes (OLEDs) determine the refresh rate in display applications, and are of great importance for practical organic displays. They also serve as an important tool in studying the transport mechanisms in organic conductors. Here, the modulation characteristics of several conventional small-molecule OLED structures [consisting of ITO/PEDOT:PSS(50 nm)/TPD(50 nm)/Alq₃(various)/LiF(1 nm)/Al(90 nm)] are measured and analyzed in terms of mobility in and thickness of the Alq ₃ layer. Their optical response was shown to be limited by electron transport across the Alq₃. Extracted electron mobilities were about 2-4times10^-6 cm²/Vmiddots (consistent with that reported in the literature) and near-identical values for mobility were obtained from devices of different thicknesses, suggesting that this method measures mobility independent of interface trap charging. This novel technique is a complement to large signal time of flight or delay time measurements (which can include interface and trap charging during the measurement) and can serve as a flexible method to study transport in actual devices     

Effect of Al:Ag alloy cathode on the performance of transparent organic light-emitting devices

Transparent organic light-emitting devices (TOLEDs) based on a stacked alloy cathode of LiF/Al:Ag are investigated. The devices have a structure of indium-tin-oxide (ITO)/4,4′,4′′-Tris[2-naphthyl(phenyl)amino]triphenylamine (2T-NATA) (25 nm)/N,N''-Di-[(1-naphthyl)-N,N''-diphenyl]-1,1''-biphenyl-4,4''-diamine (NPB) (40 nm)/tris-(8-hydroxyquinoline) aluminum (Alq3) (50 nm)/LiF (1 nm)/Al:Ag (1:3) (x), where the thicknesses of cathode metal layers (Al:Ag) are adjusted, respectively, from 70 nm to 100 nm. In the experiment, it is found that the LiF (1 nm)/Al:Ag (1:3) (75 nm) has good electron injection efficiency. Compared with an Al-only cathode, the turn-on voltage is lowered. At the voltage of 10 V, the luminances for bottom emission from ITO anode side and top emission from metal cathode side are 2 459 cd/m2 and 1 729 cd/m2, respectively. Thanks to electron injection enhancement by using Al:Ag cathode, we can obtain a better energy level matching between the cathode and the organic layer, thus the devices have lower turn-on voltage and higher luminance. The total transmittance of the devices can achieve about 40% at the wavelength of 550 nm.     

Tandem white organic light-emitting device using non-modified Ag layer as cathode and interconnecting layer

Tandem white organic light-emitting device (WOLED) using non-modified Ag film as cathode and interconnecting layer is demonstrated. Effective electron injection is achieved when Ag is deposited on 4,7-diphenyl-1,10-phenanthroline electron transporting layer without any modified layer. Single OLED with Ag cathode shows comparable performance to that of device with Mg:Ag cathode. Such tandem WOLED exhibits low driving voltage, high power efficiency (15.1 lm/W at 1000 cd/m²) and low efficiency roll-off. The working mechanisms of single and tandem devices were discussed in detail. These results could provide a simple method to fabricate high performance tandem white OLED.     

Colored reflective organic light-emitting device without bias

Under white ambient illumination and without bias, a reflective organic light-emitting device (ROLED) comprising a microcavity cathode exhibited various colors for static information display applications by means of internal interference and absorption effects. The configuration of this microcavity cathode was a metal/organometallic/metal structure of Al (10 nm)/Ag (15 nm)/Ag nanoparticles doped inside tris(8-hydroxyquinolinato) aluminum (Alq₃) (x nm)/Al (100 nm) with excellent conductivity. The thickness of the Ag:Alq₃ played a crucial role in determining the reflection color; for example, varying it from 20, 40, 60, 80 and 100 nm yielded the colors light yellow, light orange, reddish purple, greenish blue, and light green, respectively. In the dark, this ROLED can be used to display information with an ultra-high contrast ratio by applying on a small bias, like conventional OLED displays. Hence, this ROLED is a highly promising candidate for applications in energy-saving electronic fixed-pattern signs, logos, indicators, and manual information displays.     

NPB厚度对堆叠式白光OLED性能的影响

主要研究了NPB厚度对堆叠式白色有机电致发光器件性能的影响。实验制备了四组结构为ITO/2-TNATA(15 nm)/NPB(Tnm)/ADN(30 nm):TBPe(2%):DCJTB(1%)/Alq3(20 nm)/LiF(1 nm)/Al(100 nm)(其中T分别为15,30,35和40 nm)的OLED器件,比较了不同厚度情况下OLED器件的电致发光特性,结果表明:改变NPB(4,4-N,N-bis-N-1-naphthy1-N-pheny1-amino-bipheny1)的厚度能够明显提高器件的发光亮度和发光效率,并调节载流子复合区域的位置,有效提高载流子的注入效果。同时发光器件的颜色也可通过调节NPB层的厚度来改变,这种器件使用NPB作为空穴传输层显示出了色纯度高、亮度好、效率较高的白光发射,其具有CIE色坐标(x=0.301 6,y=0.338 5),最高亮度和最大发光效率分别达到14 020 cd/m2与2.94 lm/W。