High efficiency rubrene based inverted top-emission organic light emitting devices with a mixed single layer

Inverted top-emission organic light emitting devices (TEOLEDs) with a mixed single layer by mixing of electron transport materials (PyPySPyPy and Alq₃), hole transport material (α-NPD) and dope material (rubrene) were investigated. Maximum power efficiency of 3.5 lm/W and maximum luminance of 7000 cd/m² were obtained by optimizing the mixing ratio of PyPySPyPy:Alq₃:α-NPD:rubrene=25:50:25:1. Luminance and power efficiency of mixed single layer device were two times improved compared to bi-layer heterojunction device and tri-layer heterojunction device. Lifetime test also shows that the mixed single layer device exhibits longer operational lifetimes of 343 h, which is three times longer than the 109 h for tri-layer device, and two times longer than the 158 h for bi-layer device. In addition, the maximum luminance and power efficiency were obtained at 20,000 cd/m² and 7.5 lm/W, respectively, when a TPD layer of 45 nm was capped onto the top metal electrode.     

High power efficiency in single layer blue phosphorescent organic light-emitting diodes

High efficiency single layer blue phosphorescent organic light-emitting diodes (PHOLEDs) without any charge transport layer were developed. A mixed host of spirobifluorene based phosphine oxide (SPPO13) and 1, 1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) was used as the host in the emitting layer. A high maximum external quantum efficiency of 15.8% and a quantum efficiency of 8.6% at 1000 cd/m² were achieved in the single-layer blue PHOLEDs without any charge transport layer. The maximum power efficiency and power efficiency at 1000 cd/m² were 31.4 and 16.9 lm/W, respectively.     

Increased luminance of MEH-PPV and PFO based PLEDs by using salmon DNA as an electron blocking layer

The effect of salmon DNA-CTMA as an electron blocking layer (EBL) has been examined on the performance of MEH-PPV and PFO-based light emitting diodes. Though the turn-on voltage increases with incorporation of EBL, a significant increase in luminance and luminous efficiency for both the devices is observed. The EBL improves the device performance by blocking electrons at the EBL-polymer interface, thereby increasing the recombination probability of electrons and holes. The luminance of the MEH-PPV based Bio-LED increases to 100 cd/m² from 30 cd/m² while a corresponding increase for the PFO based LED is to 160 cd/m² from 80 cd/m² with and without EBL, respectively.     

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.     

具有新型双空穴注入层的有机发光二极管

采用新型双空穴注入层N, N, N', N'-tetrakis(4-Methoxy-phenyl)benzidine/Copper phthalocyanine(MeO-TPD/CuPc)及器件结构:ITO/MeO-TPD(15 nm)/CuPc(15 nm)/ N, N'-Bis(naphthalen-1-yl)-N, N'-bis(phenyl)benzidine (NPB, 15 nm)/8-hydroxyquinoline (Alq₃, 50 nm)/LiF(1 nm)/Al(120 nm), 研制出高效有机发光二极管(器件D), 与其他器件(器件A, 没有空穴注入层的器件; 器件B, MeO-TPD单空穴注入层; 器件C, CuPc单空穴注入层)相比, 其性能得到明显改善. 器件D的起亮电压降至3.2 V, 比器件A, B, C的起亮电压分别降低了2, 0.3, 0.1 V. 器件D在10 V时, 其最大亮度为23893 cd/m², 最大功率效率为1.91 lm/W, 与器件A, B, C的最大功率效率相比, 分别提高了43% (1.34 lm/W), 22% (1.57 lm/W), 7% (1.79 lm/W). 性能改善的主要原因是由于空穴注入和传输性能得到了改善, 通过单空穴型器件的J-V 曲线对这一现象进行了分析. 关键词： 有机发光二极管 空穴注入层 功率效率 势垒     

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％...     

Simplified hybrid white organic light‐emitting diodes with efficiency/efficiency roll‐off/color rendering index/color‐stability trade‐off

A high‐performance hybrid white organic light‐emitting diode (WOLED) based on a simple structure has been developed. The resulting device exhibits a maximum total current efficiency and power efficiency of 35.7 cd/A and 30.6 lm/W, respectively. Even at a high luminance of 1000 cd/m², a current efficiency of 32.0 cd/A and a power efficiency of 19.4 lm/W are obtained, suggesting that the device exhibits a low efficiency roll‐off. Besides, the device shows excellent color‐stability during a wide range of luminance and a high color rendering index (CRI) of 83 is obtained. Moreover, the origin of the superior properties is explored comprehensively. Such achieved results demonstrate that high efficiency, low efficiency roll‐off, stable color and high CRI can be simultaneously realized in a simplified hybrid WOLEDs. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

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%。     

The use of a perylenediimide derivative as a dopant in hole transport layer of an organic light emitting device

A perylene diimide (PDI) derivative was used as a dopant in the hole transport layer (HTL) of an organic light emitting device. The HTL examined was poly (N-vinylcarbazole) (PVK) and the PDI used was N,N′-di-dodecylperylene-3,4,9,10-bis-(dicarboximide), (N-DODEPER). The structure of the device was ITO/PEDOT:PSS (70 nm)/PVK:N-DODEPER(0, 0.2, 0.4, 0.8 wt.%) (65 nm)/Alq₃ (35 nm)/LiF (1.3 nm)/Al (100 nm). 0.8 wt.% N-DODEPER presence exhibited a luminous efficiency of 7.87 cd/A and an external quantum efficiency of 0.78% at 21 mA/cm² and a power efficiency of 3l m/W at 12 mA/cm². The luminous and power efficiency values were significantly enhanced by a factor of 15 with respect to that of undoped device.     

稳定的蓝色及白色有机薄膜电致发光器件

报道了一种稳定的蓝色和白色有机薄膜电致发光器件,蓝色器件最大亮度为7526cd／m^2,最大效率1．451m／W,半亮度寿命1035h(初始亮度l00cd／m^2)。白色器件的最大亮度为14850cd／m^2,最大效率2．881m／W,色度x=0．31,y=0．38,且色度不随电流增大而变化,半亮度寿命为2860h(初始亮度100cd／m^2)。     

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.     

Low driving voltage in white organic light-emitting diodes using an interfacial energy barrier free multilayer emitting structure

The driving voltage of white organic light-emitting diodes (WOLEDs) with blue fluorescent and red phosphorescent emitting materials was lowered by using a device architecture with little energy barrier between emitting layers. A mixed layer of hole and electron transport materials was used as a host material and an interlayer, reducing the driving voltage of WOLEDs. The driving voltage of WOLEDs was reduced by more than 4 V and power efficiency of WOLEDs was improved by more than 40% due to little energy barrier for holes and electrons injection in light-emitting layer. In addition, there was little change of electroluminescence spectra from 100 to 10,000 cd/m².     

A comparative study of electrode effects on the electrical and luminescent characteristics of Alq3/TPD OLED: Improvements due to conductive polymer (PEDOT) anode

The performance of organic light emitting device (OLED) structures, based on identically fabricated Alq₃/TPD active regions, with various anode and cathode electrode structures are compared, and performance differences related to the different anode structure. The best performance was achieved with a conductive polymer, 3,4-polyethylenedioxythiopene-polystyrenesultonate (PEDOT), used as an anode layer, yielding a brightness of 1720 cd/m² at 25 V, a turn-on voltage of 3 V, and electroluminescence (EL) efficiency and external quantum efficiency of 8.2 cd/A and 2%, respectively, at a brightness of 100 cd/m² and 5 V. Compared to a baseline device (TPD/Alq₃/Al), PEDOT anodes substantially reduce the turn-on voltage and made current injection almost linear after turn-on, whiles devices incorporating a LiF and CuPc layers significantly improved device efficiency while slightly improving turn-on voltage and maintaining superlinear I-V injection. This is attributed to the reduced barrier at the organic-organic interface in PEDOT, the ‘ladder’ effect of stepping the band offset over several interfaces, and the favorable PEDOT film morphology. The benefit of the PEDOT anode is clearly seen in the improvement in device brightness and the high external quantum efficiency obtained.     

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.     

Efficient bright white organic light-emitting diode based on non-doped ultrathin 5,6,11,12-tetraphenylnaphthacene layer

High-performance undoped white organic light-emitting diode (OLED) has been fabricated using an ultrathin yellow-emitting layer of 5,6,11,12-tetraphenylnaphthacene (rubrene) inserted at two sides of interface between two N,N′-bis-(1-naphthyl)-N,N′- biphenyl-1,1′-biphenyl-4,4′- diamine (NPB) layers as a hole transporting and blue emissive layer, respectively. The results showed that a maximum luminance of the device reached to as high as 21,500 cd/m² at 15 V. The power efficiencies of 2.5 and 1.6 lm/W at a luminance of 1000 and 10000 cd/m², respectively, were obtained. The peaks of electroluminescent (EL) spectra locate at 429 and 560 nm corresponding to the Commissions Internationale De L’Eclairage (CIE) coordinates of (0.32, 0.33), which is independent of bias voltage. The performance enhancement of the device may result from direct charge carrier trapping in rubrene. Energy transfer mechanism was also found in the EL process.     

Efficient white organic light-emitting diodes based on an orange iridium phosphorescent complex

Stable and efficient white light emission is obtained by mixing blue fluorescence and orange phosphorescence. The introduction of double exciton blocking layers brings about well confinement of both charge-carriers and excitons in the emission layer. By systematically adjusting blue fluorescent and orange phosphorescent emission layers thickness, carriers in emission zone are balanced, and electrically generated excitons can be efficiently utilized. One white device with power efficiency of 14.4 lm/W at 100 cd/m² has excellently stable spectra. The improvement of performance is attributed to efficient utilization of the excitons and more balance of charge-carriers in emission layer.     

陶瓷基片薄膜电致发光器件

本文报道了一种新颖的陶瓷基片薄膜电致发光器件(CSTFEL),使用高介电常数的陶瓷片作器件的基片,同时又作为器件中的绝缘层,陶瓷片表面无需抛光处理,直接制作发光器件,工艺简单,用市电50Hz,220V驱动,亮度大于30cd/m2,寿命大于10000小时.     

Effect of thickness variation of hole injection and hole blocking layers on the performance of fluorescent green organic light emitting diodes

In this paper we present the effect of thickness variation of hole injection and hole blocking layers on the performance of fluorescent green organic light emitting diodes (OLEDs). A number of OLED devices have been fabricated with combinations of hole injecting and hole blocking layers of varying thicknesses. Even though hole blocking and hole injection layers have opposite functions, yet there is a particular combination of their thicknesses when they function in conjunction and luminous efficiency and power efficiency are maximized. The optimum thickness of CuPc (Copper(II) phthalocyanine) layer, used as hole injection layer and BCP (2,9 dimethyl-4,7-diphenyl-1,10-phenanthroline) used as hole blocking layer were found to be 18 nm and 10 nm respectively. It is with this delicate adjustment of thicknesses, charge balancing is achieved and luminous efficiency and power efficiency were optimized. The maximum luminous efficiency of 3.82 cd/A at a current density of 24.45 mA/cm² and maximum power efficiency of 2.61 lm/W at a current density of 5.3 mA/cm² were achieved. We obtained luminance of 5993 cd/m² when current density was 140 mA/cm². The EL spectra was obtained for the LEDs and found that it has a peaking at 524 nm of wavelength.     

Characterization of two-emitter WOLED with no additional blocking layer

In this paper, white organic light emitting diodes (WOLEDs) utilizing two primary-color emitters with no additional blocking layer are fabricated. With a structure of ITO/2TNATA (20 nm)/NPB (20 nm)/NPB: rubrene (2%) (10 nm)/ADN (30 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al (100 nm), a white light with CIE coordinates of (0.344, 0.372) is generated at a current density of 30 mA/cm² and the electroluminescence (EL) spectra consist of two broad bands around 456 nm (ADN) and 556 nm (NPB:rubrene). The device shows the low turn-on voltage and bright white emission with a power efficiency of 2.3 lm/W at a luminance of 100 cd/m². Through control of the location of the recombination zone and energy transfer, a stable white light emission is achieved. The maximum color shift is less than 0.02 units on the 1931 CIE x,y chromaticity diagram. Given the spectral power distribution of WOLED, the parameters of a light source (chromaticity coordinate, CCT, CRI, and the luminous efficacy) can be calculated. A MATLAB program for this purpose is developed in this paper. Based on this, the design of WOLED for an illumination and display system using a white emitter with color filter arrays is discussed.     

Electrophosphorescent devices with solution processible emitter and hole transport layer stack

The light emitting behavior of the electrophosphorescent devices with solution-processible hole transport layer and light emitting layer was characterized. We have introduced the hole-transporting stacked layer composed of poly(3,4-ethylenedioxy thiophene): poly(4-styrenesulfonate) [PEDOT:PSS] and thin perfluorinated ionomer, aiming for the improvement of charge injection and transport with corresponding high efficiency behavior. In order to provide a suitable work function, composition and thickness of the ultra-thin perfluorinated ionomer was optimized for being an interfacial layer condition; 34 cd/A of green phosphorescent device was obtained while the control device without ionomer shows the luminous efficiency of 29 cd/A. Both for devices with vacuum-deposited and solution-processed electrophosphorescent emitters, change of the device efficiencies were analyzed in terms of the work function, surface chemical composition, and charge conduction behavior.