Phosphorescent white organic light-emitting diodes with stable white color depending on luminance

We fabricated simple and color-stable phosphorescent white organic light-emitting diodes (OLEDs) without an interlayer using a single host of 1,3-bis(9-carbazolyl)benzene with iridium(III) bis[(4,6-difluorophenyl) pyridinato-N,C2’]picolinate and bis(1-phenylisoquinoline)(acetylacetonate) iridium(III) as blue and red phosphorescent emitters, respectively. The CIE 1931 color coordinate difference of the white OLEDs is (0.008, 0.007) when the luminance of the device is increased from approximately 265 cd/m² to 9156 cd/m², which is regarded as visually indistinguishable in practice. In addition, we also measured the decay time of excitons to investigate the emission mechanism in this device using transient photoluminescence and electroluminescence techniques.     

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.     

White organic electroluminescence from fluorescent bis (2-(2-hydroxyphenyl) benzoxazolate)zinc doped with phosphorescent material

Efficient white electroluminescence has been obtained by using an electroluminescent layer comprising of a blue fluorescent bis (2-(2-hydroxyphenyl) benzoxazolate)zinc [Zn(hpb)₂] doped with red phosphorescent bis (2-(2′-benzothienyl) pyridinato-N,C^3′)iridium(acetylacetonate) [Ir(btp)₂acac] molecules. The color coordinates of the white emission spectrum was controlled by optimizing the concentration of red dopant in the blue fluorescent emissive layer. Organic light-emitting diodes were fabricated in the configuration ITO/α-NPD/Zn(hpb)₂:0.01 wt%Ir(btp)₂acac/BCP/Alq₃/LiF/Al. The J-V-L characteristic of the device shows a turn on voltage of 5 V. The electroluminescence (EL) spectra of the device cover a wide range of visible region of the electromagnetic spectrum with three peaks around 450, 485 and 610 nm. A maximum white luminance of 3500 cd/m² with CIE coordinates of (x, y=0.34, 0.27) at 15 V has been achieved. The maximum current efficiency and power efficiency of the device was 5.2 cd/A and 1.43 lm/W respectively at 11.5 V.     

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.     

Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye

Organic optoelectronic integrated devices(OIDs) with ultraviolet(UV) photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence(TADF) material 4, 5-bis(carbazol-9-yl)-1, 2-dicyanobenzene(2 CzPN) as host. The OIDs doping with typical red phosphorescent dye [tris(1-phenylisoquinoline)iridium(Ⅲ), Ir(piq)_3], orange phosphorescent dye {bis[2-(4-tertbutylphenyl)benzothiazolato-N,C~(2')]iridium(acetylacetonate),(tbt)_2 Ir(acac)}, and blue phosphorescent dye [bis(2, 4-di-fluorophenylpyridinato)-tetrakis(1-pyrazolyl)borate iridium(Ⅲ), FIr6] were investigated and compared. The(tbt)_2 Ir(acac)-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the(tbt)_2 Ir(acac)-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m~2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10~(11) Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.     

高效、色度稳定的顶发射白光有机发光二极管

顶发射白光有机发光二极管(white organic light-emitting diodes,WOLEDs)因可与有源驱动电路结合实现大开口率和高分辨率,因而在白光照明和全彩显示中有着良好的应用前景．本文制备了红/蓝双磷光发光层的顶发射WOLEDs,通过在红光层与蓝光层间插入电子阻挡层tris(phenypyrazole)iridium(Ir(ppz)₃),降低了对红光掺杂浓度的要求,红光掺杂浓度的提高不仅降低了对制备工艺的要求,提高了工艺可重复性,而且改善了WOLEDs的效率与色度稳定性。分析了色度稳定的原因,优化了红光和蓝光磷光客体的掺杂浓度,制备出发光效率达到7.9 cd·A-1的顶发射WOLED,其色坐标位于暖白光区,在87～2 402 cd·m-2亮度范围内色度很稳定,仅变化(0.006,0.01)。     

An organic light-emitting device with ultrathin quantum-well structure as light emitting layer

Both phosphorescent materials and devices, which emit red and green light, already have great performance and breakthrough. The biggest challenge and bottleneck is the blue phosphorescent device, if we want to popularize phosphorescent organic light-emitting device (OLED) in the full-color panel. This paper brings a new quantum-well structure in light-emitting layer. We select the commonly used phosphor materials, N,N′-dicarbazoly-2,5-benzene (mCP) and bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III) (FIrpic). The structure of the device is indium-tin oxide (ITO)/N,N′-bis(naphthalene-1-y1)-N,N′-bis(phenyl)-benzidine (NPB)/di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC)/mCP/FIrpic/mCP/4,7-dipheny1-1,10-phenanthroline (Bphen)/Mg:Ag. The blue OLED of good performance is achieved by adjusting the thickness of FIrpic. When the thickness of FIrpic is 0.2 nm and the Current density is 34.86 mA/cm², the results show that the luminance of the device is 1000 cd/m², then the luminous power efficiency of the device is 6.01 lm/W. Meanwhile, the light emitting mechanism of ultrathin quantum-well structure is well studied, the quantum confinement effect and the role of quantum well structure as the light-emitting layer in the blue phosphorescent devices are mainly analyzed.     

Efficient white polymer light-emitting diodes based on a phosphorescent iridium complex and a fluorescent silole and carbazole copolymer

White polymer light-emitting diodes (WPLEDs) were fabricated with blue phosphorescent iridium bis(2-(4,6-difluorophenyl)-pyridinato-N,C²′) picolinate (FIrpic) and red fluorescent silole and carbazole copolymer PCz-MPTST within a poly(N-vinylcarbazole) (PVK): 1,3-bis[(4-tert-butylphenyl)-1,3,4- oxadiazolyl] phenylene (OXD-7) host matrix. Efficient white emission consisting two emission peaks was achieved with luminous efficiency of 9.2 cd/A and CIE coordinates of (0.37, 0.40). By means of transient photoluminescence response, energy transfer among the blending components was investigated and discussed.     

不同主体双发光层白色有机电致发光器件的性能研究

制备了结构为ITO/NPB/CBP:TBPe:rubrene/BAlq:Ir(piq)₂(acac)/BAlq/Alq₃/Mg:Ag的白色磷光有机电致发光器件.利用两种不同的主体材料,即用双载流子传输型主体材料CBP掺杂荧光染料TBPe及rubrene作为蓝光和橙黄光发光层;用电子传输型主体材料BAlq掺杂磷光染料Ir(piq)₂(acac)作为红色发光层.以上双发光层夹于空穴传输层NPB与具有电子传输性的阻挡层BALq之间.讨论了如何控制 关键词： 有机电致发光 磷光染料 掺杂 白光     

High-efficiency blue and white phosphorescent organic light-emitting devices

We have significantly improved the efficiency of blue and white phosphorescence from organic light-emitting devices (OLEDs) based on phosphorescent iridium complexes. To improve the emission efficiency, 4,4^′-Bis(9-carbazolyl)-2,2^′-Dimethyl-biphenyl (CDBP), which has a high triplet energy, was used as the carrier-transporting host for the emissive layer. The blue phosphorescent OLED exhibited a maximum external quantum efficiency of 10.4%, which corresponds to a current efficiency of 20.4 cd/A. This result can be explained as due to the efficient confinement of triplet energy on blue phosphorescent molecules, which is consistent with the results of transient photoluminescence experiments. The white phosphorescent OLED with greenish-blue and red emissive layers exhibited a maximum external quantum efficiency of 12% and a luminous efficiency of 18 cd/A. This is primarily attributed to the improvement of greenish-blue emission efficiency as well as the emission efficiency of the blue phosphorescent OLED.     

双极性主体材料9-phenyl-3-(phenylsulfonyl)-6-(triphenylsilyl)-9H-carbazole的合成及其光电性质

设计开发了一种新的双极性蓝色磷光主体材料,将其搭配Firpic应用于简单器件结构,通过调整器件中载流子传输层的厚度得到了比较满意的结果:最大电流效率40 cd/A,最大亮度19 691 cd/m²,最大流明效率12 lm/W。这一结果说明所开发的主体材料能够很好的平衡载流子的注入与传输能力,具有适宜的三线态能量和良好的热稳定性,是一种优良的蓝色磷光主体材料。     

Study of different roles phosphorescent material played in different positions of organic light emitting diodes

Phosphorescent materials are crucial to improve the luminescence and efficiency of organic light emitting diodes (OLED), because its internal quantum efficiency can reach 100%. So the studying of optical and electrical properties of phosphorescent materials is propitious for the further development of phosphorescent OLED. Phosphorescent materials were generally doped into different host materials as emitting components, not only played an important role in emitting light but also had a profound influence on carrier transport properties. We studied the optical and electrical properties of the blue 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi)-based devices, adding a common yellow phosphorescent material bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2′] iridium(acetylacetonate) [(t-bt)₂Ir(acac)] in different positions. The results showed (t-bt)₂Ir(acac) has remarkable hole-trapping ability. Especially the ultrathin structure device, compared to the device without (t-bt)₂Ir(acac), had increased the luminance by about 60%, and the efficiency by about 97%. Then introduced thin 4,4′-bis(carbazol-9-yl)biphenyl (CBP) host layer between DPVBi and (t-bt)₂Ir(acac), and got devices with stable white color.     

Efficient blue phosphorescent organic light emitting diodes with host engineering

We demonstrate as much as possible blue color and high efficiency phosphorescent organic light-emitting diodes (PHOLEDs) by using well-known iridium(III)bis[(3,5-difluoro-4-cyanophenyl)-pyridinato-N,C′]picolinate (FCNIrpic) dopant and previously reported good host materials. For the control of blue color and efficiency, various host materials, 1,3-bis(carbazole-9-yl)benzene (mCP), 9-(3-(9H-carbazole-9-yl)phenyl)-3-(dibromophenylphosphoryl)-9H-carbazole (mCPPO1), and 2,8-di(9H-carbazol-9-yl)dibenzo[b,d]furan (DFCz), bis(4-(N-carbazole)phenyl)dimethylsilane (2MCBP) are selected and investigated their performances. A maximum external quantum efficiency (EQE) of 23.9% and power efficiency of 30.2 lm/W are achieved from 2MCBP device with Commision Internationale de L'Eclairage color coordinates (CIE_x,y) of (0.14, 0.21). The deepest color with color coordinate of (0.14, 0.19) is obtained for the mCP device.     

激基复合物和磷光超薄层相结合的高效率非掺杂白光有机发光二极管

将蓝光激基复合物mCP∶PO-T2T和磷光超薄层结合,分别制备了基于Ir（pq）₂acac（～0.5 nm）/mCP∶PO-T2T/Ir（pq）₂acac（～0.5 nm）结构的双色互补色和基于Ir（ppy）₃（～0.5 nm）/mCP∶PO-T2T/Ir（pq）₂acac （～0.5 nm）结构的三基色非掺杂白光有机发光二极管（White organic light emitting diodes, WOLED）,以探索超薄层在激基复合物中的应用。所制备的双色互补色WOLED,其最大电流效率、功率效率和外量子效率分别为46.1 cd/A、43.9 lm/W和22.2%,而三基色WOLED所实现的最大电流效率、功率效率和外量子效率分别为66.8 cd/A、63.5 lm/W和24.2%。研究分析表明,从高能的蓝光激基复合物发光层向两侧低能的红光和绿光磷光超薄层有效的能量传递是实现非掺杂WOLED高效率的原因。     

低效率滚降、发光颜色稳定的磷光白色有机电致发光器件

本文采用多发光层结构,制备了高亮度下具有高发光效率,同时在较宽亮度范围内发光颜色稳定的白色磷光有机电致发光器件(WOLED).在对双发光层结构磷光OLEDs的发光机制和载流子传输过程进行系统研究的基础上,将两种磷光OLEDs的发光层结构相结合,获得的多发光层结构磷光WOLED最大电流效率和外量子效率分别为34.6 cd/A和13.5%;当亮度为1000 cd/m^2时,其电流效率和外量子效率分别为33.9 cd/A和13.3%,外量子效率滚降仅为1.5%;亮度从1000 cd/m^2增至10000 cd/m^2的过程中,其CIE色度坐标从(0.342,0.403)变化至(0.326,0.392),变化量ΔCIE为(0.016,0.011).     

Efficient Solution-Processed Blue Electrophosphorescent Devices Based on a Novel Small-Molecule Host

Efficient blue small molecular phosphorescent fight-emitting diodes with a blue phosphorescent dye bis（3,5- difluoro-2-（2-pyridyl）-phenyl-（2-carboxypride） iridium （Ⅲ） （Flrpic） doped into a novel small-molecule host 9,9- bis[4-（3,6-di-tert-butylcarbazol-9-yl）phenyl] fluorene （TBCPF） as the light-emitting layer have been fabricated by spin-coating. The host TBCPF can form homogeneous amorphous films by spin-coating and has triplet energy higher than that of the blue phosphorescent dye Flrpic. All the devices with different Flrpic concentration in the emitting layer give emission from Flrpic indicating complete energy transfer from TBCPF to Flrpic. The device shows the best performance with a peak brightness of 8050 cd/m^2 at 10.2 V and the maximum current efficiency up to 3.52 cd/A, when the Flrpic doped concentration is as high as 16%.     

Deep blue organic light emitting diode based on anthracene derivative as a dopant

This letter presents a deep blue organic light emitting diode which was fabricated by using 9,10-di(2-naphthyl)anthracene as a dopant and 4,4′-N,N′-dicarbazole-biphenyl as a host. The Commission Internationale de l’Eclairage coordinates of (0.1516, 0.0836) were achieved in the cell, which is very close to the National Television Standards Committee standard of (0.14, 0.08). Meanwhile, maximum luminance over 6500 cd/cm² and maximum current efficiency of 3.5 cd/A were also obtained.     

Influence of Dopant Concentration on Electroluminescent Performance of Organic White-Light-Emitting Device with Double-Emissive-Layered Structure

A novel phosphorescent organic white-light-emitting device （WOLED） with contiguration of ITO/NPB/CBP： TBPe：rubrene/Zn（BTZ）2：Ir（piq）2（acac）/Zn（BTZ）2/Mg：Ag is fabricated successfully, where the phosphorescent dye bis （1-（phenyl）isoquinoline） iridium （Ⅲ） acetylanetonate （Ir（piq）2 （acac）） doped into bis-（2-（2-hydroxyphenyl） benzothiazole）zinc （Zn（BTZ）2） （greenish-blue emitting material with electron transport character） as the red emitting layer, and fluorescent dye 2,5,8,11-tetra-tertbutylperylene （TBPe） and 5,6,11,12-tetraphenyl-naphthacene （rubrene） together doped into 4,4＇-N,N＇-dicarbazole-biphenyl （CBP） （ambipolar conductivity material） as the blue-orange emitting layer, respectively. The two emitting layers are sandwiched between the hole-transport layer N ,N＇-biphenyl-N , N＇-bis （1-naph thyl）-（1,1＇-biphenyl）-4, 4 Cdiamine （NP B） and electron-transport layer （Zn（BTZ）2 ） The optimum device turns on at the driving voltage of 4.5 V. A maximum external quantum efficiency of 1.53%. and brightness 15000 cd/m^2 are presented. The best point of the Commission Internationale de 1＇Eclairage （CIE） coordinates locates at （0.335, 0.338） at about 13 V. Moreover, we also discuss how to achieve the bright pure white light through optimizing the doping concentration of each dye from the viewpoint of energy transfer process.     

基于mCP与UGH2为母体的双发光层高效率蓝色磷光OLED

以9,9'-(1,3-苯基)二-9H-咔唑(m CP)和1,4-二(三苯甲硅烷基)苯(UGH2)为母体,将常用的蓝光染料二(3,5-二氟-2-(2-吡啶)苯基-(2-吡啶甲酸根))合铱(Ⅲ)(FIrpic)掺入这两种母体材料中,制得具有双发光层结构的蓝色磷光有机电致发光器件,并对整个物理机制进行了阐述。该器件较基于m CP或UGH2为母体的单发光层器件有着更高的器件效率。器件的最大电流效率、功率效率、外量子效率分别为21.13 cd/A、14.97 lm/W、10.56%。器件亮度从100 cd/m2到3 000 cd/m2时,效率滚降为34.2%。     

Efficient small molecular and polymer organic devices using bis[2-(4-tert-butylphenyl)benzothiazolato-N,C′] iridium (III) (acetylacetonate) dye as emitter

Small molecular organic light-emitting diodes (MOLED) and polymer organic light-emitting diodes (POLED) were fabricated with yellow light emission phosphorescent dye bis[2-(4-tert-butylphenyl)benzothiazolato-N,C²′] iridium (III) (acetylacetonate) doped in different hosts. The electroluminescent (EL) spectra of both devices shown two peaks generated from iridium dye but the position of main peak changed and became broader for POLED. The maximum luminance of 10,500 cd/m² achieved at 12.5 V for MOLED is higher than maximum luminance of 9996 cd/m² at 20 V for POLED. The maximum power efficiency of small molecular device is 6.4 lm/W, which is higher than 2.3 lm/W of polymer device, but the efficiency of both devices will roll off at large current density.