发光层掺杂对红光OLED性能影响研究

制备高效率、高亮度的红光有机发光二极管是显示器实现全彩色的关键,对高性能的红光有机发光二极管器件研究具有十分重要的意义.本文主要研究了掺杂剂(DCJTB)浓度对红光有机发光二极管性能影响.实验采用真空热蒸镀的方法,选取结构为ITO／2-TNATA(20 nm)/NPB(30 nm)/AlQ(50 nm):(X%)DCJTB／AlQ(30 nm)／LiF(0.8 nm)／Al(100 nm)的红光器件,在高准确度膜厚控制仪的监控下,实现了有机薄膜功能材料的精确蒸镀.研究表明:红光掺杂剂掺杂浓度为(2.5~3.0)%时,在12 V电压下,可以得到发光亮度最高达到8 900 cd/m²,发光效率大于2.8 cd/A,且发光光谱波长为610~618 nm较为理想的红光有机发光二极管器件.     

White organic light-emitting diodes based on benzothiazole derivative

This paper describes the white organic light-emitting diodes (WOLEDs) made from a benzothiazole derivative, N-(4-(benzo[d]thiazol-2-yl)phenyl)-N-phenylnaphthalen-1-amine (BPNA). The bright yellowish-white emission was obtained from a non-doped triple-layer device: ITO/NPB (40 nm)/BPNA (50 nm)/Alq₃ (40 nm)/LiF/Al. The Commission Internationale de L’Eclairage (CIE) coordinates of the device were (0.24, 0.36) at 10 V. The maximum brightness of the device was 9225 cd/m² at 14.4 V. A current efficiency of 3.08 cd/A, a power efficiency of 1.21 lm/W and an external quantum efficiency of 1.18% at a driving current density of 20 mA/cm² were achieved. WOLED with a DCJTB-doped structure of ITO/TcTa/BPNA/BPNA: DCJTB (0.5%)/BPNA/BCP/Alq₃/LiF/Al was fabricated in comparison with the non-doped device. The device emitted bright white light with the CIE coordinates of (0.33, 0.29) at 10 V and a maximum luminance of 7723 cd/m² at 14.8 V.     

以蓝色发光材料DPVBi为基质的白色发光器件

白色有机发光器件是实现彩色平板显示的重要方案之一。利用蓝色发光材料DPVBi[4，4′—(2，2—苯乙烯基)—1，1′—联苯]掺杂红光染料DCJTB[4—氰甲烯基—2—叔丁基—6—(1，1，7，7—四甲基久洛尼定基—9—烯炔基—4H—吡喃)]作发光层制备了白色发光器件。研究了DPVBi掺杂不同浓度IDCJTB薄膜的光致发光性质，根据光致发光结果，制备了以DPVBi掺杂不同浓度DCJTB作发光层的电致发光器件，其结构为ITO／GuPc／NPB／DPVBi：DCJTB／Alq3／LiF／Al。当DCJTB质量分数为0．0008时，器件实现了白色发光(色度x=0．25，y=0．32)，电致发光和光致发光的掺杂比例基本相符，表明器件的白色发光主要是由基质DPVBi向掺杂剂DCJTB的能量传递产生的。研究还发现：白色器件随电压升高，光谱中蓝色成分相对于红色成分的比例略有增加，文章对此现象进行了分析。该白光器件在14V时达到最高亮度7822cd／cm^2，在20mA／cm^2电流密度下的亮度为-489cd／cm^2，最大流明效率为1．75lm／W。     

High efficiency small molecule white organic light-emitting devices with a multilayer structure

In this paper, a new white organic light-emitting device (WOLED) with multilayer structure has been fabricated. The structure of devices is ITO/N, N-bis-(1-naphthyl)-N, N^′-diphenyl-1, 1′-biphenyl-4, 4′-diamine (NPB) (40 nm)/NPB: QAD (1%): DCJTB (1%) (10 nm) /DPVBi (10 nm) /2, 9-dimethyl, 4, 7-diphenyl, 1, 10-phenanthroline (BCP) (d nm)/tris-(8-hydroxyquinoline) aluminium (Alq₃)(50-d nm)/LiF (1 nm)/Al (200 nm). In our devices, a red dye 4-(dicyanomethylene)-2-t-butyl-6 (1, 1, 7, 7-tetramethyl julolidyl-9-enyl)-4H-pyran (DCJTB) and a green dye quinacridone (QAD) were co-doped into NPB. The device with 8 nm BCP shows maximum luminance of 12 852 cd/m² at 20 V. The current efficiency and power efficiency reach 9.37 cd/A at 9 V and 3.60 lm/W at 8 V, respectively. The thickness of the blocking layer permit the tuning of the device spectrum to achieve a balanced white emission with Commission International de’Eclairage (CIE) chromaticity coordinates of (0.33,0.33). The CIE coordinates of device change from (0.3278, 0.3043) at 5 V to (0.3251, 0.2967) at 20 V that are well in the white region, which is largely insensitive to the applied bias.     

不同发光染料的顶发射有机电致发光器件的研制

通过设计合理的微腔结构,制备了基于绿光染料C545t、黄光染料Rubrene、红光染料DCJTB的3种顶发射有机电致发光器件。研究了不同发光染料对顶发射器件的光谱的影响。研究表明,微腔结构对光谱具有窄化作用。绿光、黄光器件的发光峰波长并未随视角增大而明显变化,体现出良好的光谱角度性,而红光器件却出现了明显的光谱蓝移现象。绿光器件的最大功率效率为8.7 lm/W,当电流密度为45 m A/cm2时,亮度能达到7 205 cd/m2;黄光器件的电流效率最大值为11.5 cd/A,当电流密度为48 m A/cm2时,亮度可达到3 770 cd/m2;红光器件的电流效率最大能达到3.54 cd/A,当电流密度为50 m A/cm2时,可获得1 358 cd/m2的亮度。采用合适的发光材料以及合适的器件结构,不仅可以提高顶发射器件的色纯度及发光效率,还可以改善器件发光光谱的角度依赖性。     

Efficient white organic light-emitting devices using 4,7-diphenyl-1,10-phenanthroline as block layer

A white light-emitting device has been fabricated with a structure of ITO/m-MTDATA (45 nm)/NPB (10 nm)/DPVBi (8 nm)/DPVBi:DCJTB 0.5% (15 nm)/BPhen (x nm)/Alq₃ [(55−x) nm]/LiF (1 nm)/Al, with x=0, 4, and 7. BPhen was used as the hole-blocking layer. This results in a mixture of lights from DPVBi molecules (blue-light) and DCJTB (yellow-light) molecules, producing white light emission. The chromaticity can be readily adjusted by only varying the thickness of the BPhen layer. The CIE coordinates of the device are largely insensitive to the driving voltages. When the thickness of BPhen is 7 nm, the device exhibits peak efficiency of 6.87 cd/A (3.59 lm/W) at the applied voltage of 6 V, the maximum external quantum efficiency η_ext=2.07% corresponding to 6.18 cd/A, and the maximum brightness is 18494 cd/m² at 15 V.     

白色有机发光器件及其稳定性

报道了一种稳定的白色有机薄膜电致发光器件.电流效率6cd/A,在电流密度20mA/cm²驱动下,亮度为1026cd/m²;最高亮度21200cd/m²,色度(x=0.32,y=0.40).该器件具有较平稳的效率电流关系,即具有弱的电流荧光猝灭.初始亮度100cd/m²下,半亮度寿命达22245h.     

Improvement of performance of tetraphenylporphyrin-based red organic light emitting diodes using WO3 and C60 buffer layers

One of the porphyrin derivatives, meso-tetraphenylporphyrin (TPP), has been synthesized and examined as an emitter material (EM) for efficient fluorescent red organic light-emitting diodes (OLEDs). By inserting a tungsten oxide (WO₃) layer into the interface of anode (ITO) and hole transport layer N,N′-Di-[(1-napthyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine (NPB) and by using fullerene (C₆₀) in contact with a LiF/Al cathode, the performance of devices was markedly improved. The current density–voltage–luminance (J–V–L) characterizations of the samples show that red OLEDs with both WO₃ and C₆₀ as buffer layers have a lower driving voltage and higher luminance compared with the devices without buffer layers. The red OLED with the configuration ITO/WO₃ (3 nm)/NPB (50 nm)/TPP (60 nm)/BPhen (30 nm)/C₆₀ (5 nm)/LiF (0.8 nm)/Al (100 nm) achieved the high luminance of 6359 cd/m² at the low driving voltage of 8 V. At a current density of 20 mA/cm², a pure red emission with CIE coordinates of (0.65; 0.35) is observed for this device. Moreover, a power efficiency of 2.07 lm/W and a current efficiency of 5.17 cd/A at 20 mA/cm² were obtained for the fabricated devices. The study of the energy level diagram of the devices revealed that the improvement in performance of the devices with buffer layers could be attributed to lowering of carrier-injecting barrier and more balanced charge injection and transport properties.     

Non-doped red to yellow organic light-emitting diodes with an ultrathin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer

In this letter, bright non-doped red to yellow organic light-emitting diodes (OLEDs) with ultrathin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer as the emitting layer were fabricated. It was investigated that the effect of the ultrathin DCJTB layer on the electroluminescent (EL) performance of OLEDs. The DCJTB layer was incorporated at different positions in the conventional tris(8-quinolinolato)-aluminum (AlQ)-based devices (ITO/NPB/AlQ/LiF/Al). The emission of DCJTB was dominative in the EL spectra of the devices, in which the position of 0.3 nm DCJTB layer was less than 10 nm from the NPB/AlQ interface. The EL peak emission of DCJTB shifted to blue side as DCJTB position moved gradually from AlQ to NPB layer. The highest brightness of the device with 0.3 nm DCJTB layer inserted into NPB reached 16,200 cd/m² at 15 V, with the CIE coordinates of (0.522, 0.439).     

Red organic light-emitting diodes with high efficiency,low driving voltage and saturated red color realized via two step energy transfer based on ADN and Alq3 co-host system

We demonstrated efficient red organic light-emitting diodes based on a wide band gap material 9,10-bis(2-naphthyl)anthracene (ADN) doped with 4-(dicyano-methylene)-2-t-butyle-6-(1,1,7,7-tetramethyl-julolidyl-9-enyl)-4H-pyran (DCJTB) as a red dopant and 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10(2-benzothiazolyl)quinolizine-[9,9a,1gh]coumarin (C545T) as an assistant dopant. The typical device structure was glass substrate/ITO/4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA)/N,N′-bis(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB)/[ADN:Alq₃]:DCJTB:C545T/Alq₃/LiF/Al. It was found that C545T dopant did not by itself emit but did assist the energy transfer from the host (ADN) to the red emitting dopant via cascade energy transfer mechanism. The OLEDs realized by this approach significantly improved the EL efficiency. We achieved a significant improvement regarding saturated red color when a polar co-host emitter (Alq₃) was incorporated in the matrix of [ADN:Alq₃]. Since ADN possesses a considerable high electron mobility of 3.1 × 10⁻⁴ cm²  V⁻¹ s⁻¹, co-host devices with high concentration of ADN (>70%) exhibited low driving voltage and high current efficiency as compared to the devices without ADN. We obtained a device with a current efficiency of 3.6 cd/A, Commission International d’Eclairage coordinates of [0.618, 0.373] and peak λ_max = 620 nm at a current density of 20 mA/cm². This is a promising way of utilizing wide band gap material as the host to make red OLEDs, which will be useful in improving the electroluminescent performance of devices and simplifying the process of fabricating full color OLEDs.     

Highly efficient all phosphorescent white organic light-emitting diodes for solid state lighting applications

We report highly efficient all phosphorescent white organic light-emitting diodes (OLEDs) with an exciton-confinement structure. By stacking two emissive layers (EMLs) with different charge transporting properties, effective charges as well as exciton confinements were achieved. Accordingly, efficient blue OLEDs with a peak external quantum efficiency (EQE) over 22% and power efficacy (PE) over 50 lm/W were developed by using iridium(III) bis(4,6-(difluorophenyl) pyridinato-N,C2′)picolinate (FIrpic) as an electro-phosphorescent dopant. When the optimized orange and red EMLs were sandwiched between the stacked two blue EMLs, white OLEDs with an EQE and PE of 24.3% and 45.9 lm/W at a luminance of 1000 cd/m² were obtained without the use of any out-coupling techniques. In addition, these white OLEDs exhibit a color rendering index (CRI) value of 84 with high efficacy.     

空穴传输层掺杂SrF2的高效率蓝色磷光OLED器件

通过在OLED器件的空穴传输层中掺杂不同比例的SrF2制作出了高效率蓝色磷光OLED器件.这种器件能有效提高蓝色磷光OLED器件的空穴注入与传输特性,降低器件的的工作电压,提高流明效率(19.11m/W)、电流效率(26.9 cd/A)以及亮度(22 220 cd/m2),和未经掺杂的参比器件相比,分别提高了85.4％...     

Photoluminescence and electroluminescence of a novel green-yellow emitting material-5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile

A new compound with intramolecular charge transfer (ICT) property—5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile(BNPPDC) was synthesized. The new compound was strongly fluorescent in non-polar and moderately polar solvents, as well as in thin solid film. The absorption and emission maxima shifted to longer wavelength with increasing solvent polarity. The fluorescence quantum yield also increased with increasing solvent polarity from non-polar to moderately polar solvents, then decreased with further increase of solvent polarity. This indicates both “positive” and “negative” solvatokinetic effects co-existed. Using this material as hole-transporting emitter and host emitter, we fabricated two electroluminescent (EL) devices with structures of A (ITO/BNPPDC (45 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm) and B (ITO/N,N′-diphenyl-N,N′-bis-(3-methylphenyl) (1,1′-diphenyl)4,4′-diamine (TPD) (50 nm)/BNPPDC (20 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm). The devices showed green-yellow EL emission with good efficiency and high brightness. For example, the device A exhibited a high brightness of 17400 cd/m² at a driving voltage of 11 V and a very low turn-on voltage (2.9 V), as well as a maximum luminous efficiency 3.61 cd/A. The device B showed a similar performance with a high brightness of 12650 cd/m² at a driving voltage of 13 V and a maximum luminous efficiency 3.62 cd/A. In addition, the EL devices using BNPPDC as a host and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a dopant (configuration: ITO/TPD (60 nm)/BNPPDC:DCJTB (2%) (30 nm)/TPBI (35 nm)/Mg:Ag (200 nm)) showed a good performance with a brightness of 150 cd/m² at 4.5 V, a maximum brightness of 12600 cd/m² at 11.5 V, and a maximum luminous efficiency of 3.30 cd/A.     

Efficient red light phosphorescence emission in simple bi-layered structure organic devices with fluorescent host-phosphorescent guest system

Highly efficient red phosphorescent devices comprising a simple bi-layered structure using tris(1-phenylisoquinoline)iridium (Ir(piq)₃) doped in a narrow band-gap fluorescent host material, bis(10-hydroxybenzo [h] quinolinato)beryllium complex (Bebq₂) are reported. The driving voltage to reach 1000 cd/m² is 3.5 V in Bebq₂:Ir(piq)₃ red phosphorescent device. With a dopant concentration of as low as 4%, the current and power efficiency values of 8.41 cd/A and 7.34 lm/W are obtained in this PHOLEDs, respectively. External quantum efficiency (EQE) of 14.5% is noticed in this red phosphorescent device, promising to high brightness applications.     

一种嘧啶铱（Ⅲ）配合物的结构及光电性质研究

合成了一种铱配合物（DFPPM=2-（2,4-二氟苯基）嘧啶,acac=乙酰丙酮）,利用 X 射线单晶衍射仪测定了该化合物的晶体结构。利用紫外-可见吸收光谱、发射光谱对其光物理性质进行研究。结果表明：（DFPPM）₂ Ir（acac）的单晶结构属于三斜晶系,P-1空间群,晶胞参数a=14.444 4（7）nm,b=18.047 9（10）nm,c=19.220 0（9）nm,α=113.115（5）°;,β=90.453（4）°;,γ=90.989（4）°;,V=4 607.0（4）nm³。（DFPPM）₂ Ir（acac）在二氯甲烷溶液中的发射峰为 496 nm。以（DFPPM）₂ Ir（acac）为客体材料,制备了结构为ITO/NPB（40 nm）/CBP：（DFPPM）₂Ir（acac）（质量分数10%,30 nm）/TPBi（15 nm）/Alq₃（50 nm）/Mg：Ag（150 nm,10：1）/Ag（10 nm）的器件,器件的发射峰位于494 nm,最大亮度达到21 400 cd/m²,最大电流效率为12.0 cd/A,最大功率效率为 5.4 lm/W。     

NaCl/Ca/Al as an efficient cathode in organic light-emitting devices

An efficient cathode NaCl/Ca/Al used to improve the performance of organic light-emitting devices (OLEDs) was reported. Standard N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′ biphenyl 4,4′-dimaine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq₃) devices with NaCl/Ca/Al cathode showed dramatically enhanced electroluminescent (EL) efficiency. A power efficiency of 4.6 lm/W was obtained for OLEDs with 2 nm of NaCl and 10 nm of Ca, which is much higher than 2.0 lm/W, 3.1 lm/W, 2.1 lm/W and 3.6 lm/W in devices using, respectively, the LiF (1 nm)/Al, LiF (1 nm)/Ca (10 nm)/Al, Ca (10 nm)/Al and NaCl (2 nm)/Al cathodes. The investigation of the electron injection in electron-only devices indicates that the utilization of the NaCl/Ca/Al cathode substantially enhances the electron injection current, which in case of OLEDs leads to the improvement of the brightness and efficiency.     

High-efficiency Simple Structure White Organic Light-emitting Devices Based on Rubrene Ultrathin Layer

White organic light-emitting devices (WOLEDs) were fabricated with an ultrathin layer of rubrene inserted between NPB and TPBI. With a simple three-layer structure of ITO/NPB(50 nm)/rubrene(0.1 nm)/TPBI(50 nm)/LiF/Al, a white light with CIE coordinates of (0.31, 0.30) were generated. The device gave a maximum luminance efficiency of 2.04 lm/W at 5 V. Furthermore, with a multilayer structure of ITO/m-MTDATA(30 nm)/NPB(20 nm)/rubrene(0.1 nm)/TPBI(40 nm)/Alq₃(10 nm)/LiF/Al, the device reached a maximum luminance efficiency of 4.29 lm/W at 4 V and the luminance could exceed 10 000 cd/m² at 10 V.     

彩色有机薄膜电致发光及动态矩阵显示

研究了绿色、红色、蓝色和白色4种有机薄膜电致发光器件.通过掺杂得到了高稳定性的绿色及红色器件,绿色器件的半寿命达14000小时(初始亮度100cd/m²),红色器件的半寿命为7500小时(初始亮度50cd/m²).还研究了具有空穴锁定层及非锁定层的多种不同结构和材料的蓝色及白色器件.研究表明无论蓝色还是白色器件,具有空穴锁定层的器件稳定性较差,老化过程中界面势垒的变化很大.非锁定层的蓝色及白色器件中,新材料JBEM比DPVBi有更优越的性能.JBEM构成的蓝色器件的半亮度寿命为1035小时(初始亮度100cd/m²).由JBEM构成的白色器件中,由蓝色及红色掺杂在同一层的器件得到最好的稳定性,其半亮度寿命为2800小时(初始亮度100cd/m²),而且它具有发光颜色不随电流变化而变化的特点.在稳定性改善的基础上研制成功96×60线,分辨率为2线/mm的绿色及白色矩阵显示屏,还利用选择蒸发的方法制造了彩色矩阵屏,设计和研制了驱动及控制电路,实现了动态显示.     

Red organic light emitting device based on TPP and a new host material

A novel coating method for fabrication of red OLEDs by using a new host material has been developed with the aid of a single furnace. The host material, zinc complex, was prepared from the reaction of zinc acetate and 2-methyl-8-hydroxyquinoline and after characterization by UV-vis, FT-IR, and ¹H NMR spectroscopes was used as an emitting material in the fabrication of OLEDs. Since meso-tetraphenylporphyrin (TPP) and zinc complex have a close molecular weight, both materials were evaporated from a single furnace. Devices with TPP and structures of ITO/PEDOT:PSS (55 nm)/PVK (90 nm)/zinc complex:TPP (65 nm)/Al (180 nm) were fabricated; Without TPP green and with TPP red emission was achieved. The device with 2 % TPP that doped into the zinc complex showed the purest red emission among all devices. The device showed the CIE coordinates of 0.70 and 0.28 at 14 V and a maximum luminance of about 94.2 cd/m². This new method is a promising candidate for fabrication of low cost red OLEDs with a more homogeneous layer.     

基于超薄发光层及双极性混合间隔层的白光有机发光器件研究

本文采用非掺杂超薄发光层及双极性混合间隔层结构,获得了高效、光谱稳定的白光有机发光器件.基于单载流子器件及单色蓝光有机发光器件的研究,确定了双极性混合间隔层的最佳比例;通过瞬态光致发光寿命研究,验证了不同发光材料之间的能量传递过程;得到的三波段和四波段白光有机发光器件的最高效率分别为52 cd/A (53.5 lm/W)和13.8 cd/A (13.6 lm/W),最高外量子效率分别为17.1%和11.2%.由于发光层不同颜色之间依次的能量传递结构,三波段白光有机发光器件的亮度从465到15950 cd/m~2时,色度坐标的变化?CIE仅为(0.005, 0.001);四波段白光有机发光器件的亮度从5077到14390 cd/m~2时,色度坐标的变化?CIE为(0.023, 0.012).