Enhanced Efficiency and Durability of Organic Electroluminescent Devices by Doping in Emitting Layer

Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device,which consists of a holetransport layer,an electron-transport layer and a luminescent layer.The holetransport layer is a N,N‘-bis(3-methyphenyl)-N,N‘-diphenylenzidine film,The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant.The doed device demonstrated a brighness in excess of 40000cd/m^2 and the maximum external quantum efficiency of 3.4%,which is about six times and four times respectively greater than those of the undoped device,For no packaged deviced,a luminance half-life on the order of about 230h has been achieved under a constant current density of 15mA/cm^2,starting at 500cd/m^2 at the room temperature.     

掺杂聚合物薄膜黄绿发光二极管

在具有电致发光的有机聚合物薄膜ｐｏｌｙ(２－ｍｅｔｈｙｏｘｙ－５－ｅｔｈｙｌｏｘｙ)－４－ｄｉ－(２－ｍｅｔｈｙｏｘｙ－５－ｏｃｔａｏｘｙ)－ｐｈｅｎｙｌｏｎｅ－ｖｉｎｙｌｅｎｅ(简称 ＭＥＭＯ－ＰＰＶ)中掺入一种高荧光量子效率的染料罗丹明６Ｇ(Ｒ６Ｇ),用旋转涂敷的方法获得了发光层,同时将其作为空穴传输层,以８－羟基＠$铝(８－Ａｌｑ３)作为电子传输层,得到了多层有机发光二极管ＩＴＯ/ＰＰＶ:Ｒ６Ｇ/Ａｌｑ３/Ａｌ．该器件峰值波长为５５０ｎｍ,发黄绿光．研究结果表明:不同掺杂浓度对器件发光光谱产生较大影响;通过掺杂,可显著提高器件的稳定性．在１８Ｖ下,器件的亮度达到３６００ｃｄ/ｍ２,外量子效率达３．２%．     

High efficiency organic light-emitting diodes using CuOx/ Cu dual buffer layers

A tunable dual-wavelength fiber Bragg grating(FBG)laser based on a distributed feedback(DFB)laser injection is proposed and experimentally demonstrated.The wavelength spacing can be tuned by adjusting the operation temperature of the DFB laser.When the DFB works at 25℃,a dual-wavelength simultaneous oscillation at 1 549.67 nm and1 553.44 nm with wavelength spacing of 3.77 nm is achieved.Our experimental results demonstrate the new concept of dual-wavelength lasing with a DFB laser injection and the technical feasibility.     

High Tg hole transport polymers for the fabrication ofbright and efficient organic light-emitting devices with an air-stablecathode

An organic electroluminescent device with a luminous efficiency of 20 Im/W, at 14 cd/m², and an external quantum efficiency of 4.6% has been fabricated using a high T_g hole transport polymer, a small molecule emission layer, and a LiF/Al cathode. The device quantum efficiency can be increased by tuning the ionization potential of the hole-transport moieties. When tested under pulsed voltage mode, in air at room temperature, and without any encapsulation, the device showed a high peak brightness of 4.4×10⁶ cd/m² at 100 A/cm² and an efficiency of 4.4 cd/A     

Molecular Doped Polymer Light Emiting Diodes with Air－stable Aluminum as Cathode

ＭｏｌｅｃｕｌａｒＤｏｐｅｄＰｏｌｙｍｅｒＬｉｇｈｔＥｍｉｔｉｎｇＤｉｏｄｅｓｗｉｔｈＡｉｒ－ｓｔａｂｌｅＡｌｕｍｉｎｕｍａｓＣａｔｈｏｄｅ①②ＣＨＥＮＢａｉｊｕｎ，ＨＯＵＪｉｎｇｙｉｎｇ．ＸＵＥＳｈａｎｈｕａ，ＬＩＵＳｈｉｙｏｎｇ（ＳｔａｔｅＫｅｙ...     

Effect of different processing methods for the hole transporting layer on the performance of double layer organic light-emitting devices

The hole transporting layer （HTL） of organic light-emitting device （OLED） was processed by vacuum deposition and spin coating method, respectively, where N,N＇-biphenyl-N, N＇-bis（3-methylphenyl）- 1, l＇-biphenyl-4,4＇ -diamine （TPD） and poly （vinylcarbazole） （PVK） acted as the hole-transport materials. Tris-（8-hydroxyquinoline）- aluminum （Alq3） was utilized as both the light-emitting layer and the electron transporting layer. The basic structure of the device cell was： indium-tin-oxide （1TO）/PVK ： TPD/Alq3/Mg：Ag. The electroluminescent （EL） characteristics of devices were characterized. The results showed that the peak of EL spectra was located at 530 nm, which conformed to the characterizing spectrum of Alq3. Compared with using vacuum deposition method, the green emission with a maximum luminance up to 26135 cd/m2 could be achieved at a drive voltage of 15 V by selecting proper solvent using spin-coating technique, and its maximum lumi nance efficiency was 2.56 lm/W at a drive voltage of 5.5 V.     

高亮度微腔有机电致发光器件

为了实现有机电致发光器件(OLED)发射光谱的窄化和高亮度,真空热蒸镀具有不同微腔结构的OLED(MOLED):玻璃衬底/分布式布拉格反射器(DBR)(1～4对的SiO2/Ta2O5层)/ITO/空穴传输层(HTL,α-NPD)/发光层(EML,Alq3:Rubrene或Alq3:Coumarin6)/电子传输层(ERL,Alq3)LiF/Mg/Ag,其中沉积DBR结构采用电子束沉积法。实验表明:该MOLED的发射光谱半波长宽度(FWHM)随DBR层数的增加而减小至最小值10nm;并且在2层DBR时,掺杂Rubrene器件得到更大的电流效率,约20cd/A,最大亮度为2.6×105cd/m2。研究发现,蓝光MOLED能够对自发光产生吸收现象,降低了出光效率。     

High efficiency green phosphorescent top-emitting organic light-emitting diode with ultrathin non-doped emissive layer

Ultrathin non-doped emissive layer (EML) has been employed in green phosphorescent top-emitting organic light-emitting diodes (TOLEDs) to take full advantages of the cavity standing wave condition in a microcavity structure. Much higher out-coupling efficiency has been observed compared to conventional doped EML with relatively wide emission zone. A further investigation on dual ultrathin non-doped EMLs separated by a special bi-layer structure demonstrates better charge carrier balance and improved efficiency. The resulting device exhibits a high efficiency of 125.0 cd/A at a luminance of 1000 cd/m² and maintains to 110.9 cd/A at 10,000 cd/m².     

Effective hole-injection layer for non-doped inverted top-emitting organic light-emitting devices

Non-doped inverted top-emitting organic light-emitting diode with high efficiency is demonstrated through employing an effective hole-injection layer composed of MoO_x. One reason for high efficiency lies on the energy-level matching between MoO_x and hole-transport, and another is due to the Ohmic contact formed between MoO_x and Ag. Both of them lead to an improvement of the hole-injection capability from Ag top anode. Moreover, the symmetrical current of “hole-only” device with MoO_x shows better hole-injection capability, which is independent of the deposition sequence. The optimized device with MoO_x hole-injection layer exhibits maximum current efficiency of 3.7 cd/A at a raised luminance level of 14,900 cd/m² and a maximum luminance of 47,000 cd/m² under 18 V.     

Electroluminescent devices using a high-temperature stableGaN-based phosphor and thick-film dielectric layer

Red, green, and blue light emission has been obtained from electroluminescent devices on glass using a high-temperature stable (HTS) GaN-based phosphor doped with rare earths (Eu, Er, Tm) and a screen-printed thick-film dielectric layer. The thick-dielectric electroluminescent (TDEL) structure consists of metal/dielectric/GaN/indium-tin-oxide/Corning 1737 glass. The BaTiO₃-based ~20-40 μm thick-film dielectric layer has a dielectric constant of ϵ_r~500-1000 and breakdown voltage >300 V. Despite granularity of the dielectric layer, the emission is uniform to well-below pixel dimensions (<10 μm). Red GaN:Eu TDEL operated at 240 V and 1 kHz exhibits a luminance of 35-40 cd/m². Under 140 lux illumination, the TDEL device structure exhibits a contrast ratio of 5:1 at 120 V, 1 kHz biasing, without the assistance of contrast-enhancement techniques. Accelerated aging tests of TDEL devices show 60 Hz operating lifetimes exceeding 1000 h at >95% brightness. The TDEL structure has advantages over current thin-film and thick-dielectric electroluminescent structures in flat panel display applications     

利用石墨烯掺杂在NPB中的OLED性能研究

采用NPB掺杂石墨烯作为空穴传输层,制备有机电致发光器件(OLED),器件结构为ITO/NPB:Graphene(20wt.%)(50nm)/Alq3(80nm)/LiF(0.5nm)/Al(120nm)。将其与标准器件ITO/NPB(50nm)/Alq3(80nm)/LiF(0.5nm)/Al(120nm)作性能比较,研究石墨烯对OLED性能的影响。结果表明,在NPB中掺杂石墨烯薄层的器件,在同等条件下性能最佳,当电流密度为90mA/cm2时器件电流效率达到最大值3.40cd/A,与标准器件最高效率相比增大1.49倍;亮度在15V时达到最大值10 070cd/m2,比标准器件最大亮度增大5.16倍。     

Efficient white organic light-emitting device based on a thin layer of hole-transporting host with rubrene dopant

A white organic light-emitting device (WOLED) in which a yellow fluorescent dye, rubrene (5,6,11,12-tetraphenylnaphthacene), is doped into a thin layer of traditional hole-transporting material NPB {4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl} is fabricated. The device has a simple structure of indium tin oxide (ITO)/CuPc/NPB/NPB: 0.7 wt.% rubrene/TPBI/lithium fluoride (LiF)/Al, where CuPc (copper phthalocyanine) and TPBI {2,2′,2″-(1,3,5-benzenetriyl)tris[1-phenyl-1H-benzimidazole]} are used as the hole-injecting layer and electron-transporting and hole-blocking layer, respectively. The device exhibits peak efficiency of 3.7 cd/A (2.1 lm/W) at 5.5 V and maximum brightness of 8200 cd/m² at 20 V. The Commission Internationale de l’Eclairage (CIE) coordinates of (0.291, 0.303) are determined at 6 V. When the bias increased from 6 V to 14 V, the colour coordinates shifted only by 2%, which is presumably related closely to the thickness of the doped NPB layer. Besides, the electroluminescent (EL) efficiency can also be improved by decreasing the thickness of the doped NPB layer. The mechanisms of generating stable white colour and improving EL performances are also discussed.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

高效叠层有机电致发光器件

采用Cs2CO3:Alq3/MoO3作电荷产生层,制备出高效双单元串联型叠层有机发光器件.双单元叠层有机发光器件发光性能受电荷产生层MoO3的厚度影响很大.当MoO3厚度为30 nm时,叠层器件表现出最好的器件性能,最大电流效率达到14.5 cd/A.在相当宽的低电流密度范围内,30 nm MoO3叠层器件的电流效率是...     

DCJTB掺杂浓度对OLED器件性能的影响(英文)

通过在发光层ADN∶TBPe∶DCJTB中改变DCJTB的掺杂浓度,得到了一种高效的白光OLED器件。考察了同一掺杂浓度TBPe下不同浓度的DCJTB的器件性能,发现当DCJTB掺杂浓度为1%(质量分数)时,器件获得最大电流效率6.6cd/A和最大功率效率3.21lm/W,此时亮度为10520cd/m2,对应的CIE坐标为(0.3186,0.3520)。通过改变DCJTB浓度,能够获得不同的器件颜色。     

Achieving above 30% external quantum efficiency for inverted phosphorescence organic light-emitting diodes based on ultrathin emitting layer

High efficiency inverted phosphorescence organic light-emitting diodes (PhOLEDs) based on ultrathin undoped and doped emitting layer (EML) have been developed. Compared to conventional device, the inverted PhOLED with 0.5 nm undoped EML exhibits significantly larger external quantum efficiency (EQE), due to effective energy transfer from the excited host to the emitter. According to the atomic force microscopy image of EML, the 0.5 nm emitter sandwiched by two hosts can be considered as the emitter doped in two hosts. The inverted device with intentionally doped ultrathin EML (1.5 nm) exhibits the maximum EQE of 31.1%, which is attributed to optimized charge balance and preferred horizontal orientation of emitter. However, such inverted device has large efficiency roll-off at high brightness because of triplet–triplet annihilation process within the ultrathin EML. This can be improved by broadening the doped EML. The inverted device with 10.5 nm doped EML has about EQE of 20 % at 10,000 cd/m². It is expected that our inverted PhOLED will promote development of high efficiency active-matrix organic light-emitting diodes based on the n-type Indium Gallium Zinc Oxide thin film transistor.     

Moiecuiar Doped Poiymer Light Emitting Diodes with Air—stabie Aluminum as Cathode

By using air-stable alumminum as cathode,molecular doped polymer (MDP)blue light emitting diodes(LEDs)were constructed.Poly(N-vinylcarbazole(PVK)doped with,1,1,4,4-tetrapheny 1-1,3-butadiens(TPB)was used as the light-emitting layer,a layer of 2-(4-biphenylyl)-5-(4-terbutypheny)1-3,4-oxadiazole(PBD) as hole-blocking,electron-transporting layer and a layer of tris(8-quinolinolate)-Aluminum(Alq3)film also worked as an electron-transporting layer.The device with structure of ITO/PVK;TPB/PBD/Alq3/Al was fabricated.Blue emis-sion began at about 4V,more than 1000 cd/m^2 was achieved at 14V.This is the lowest turn-on voltage for polymeric lgiht-emitting diodes(PLEDS)used air-stable elec-trodes.Such low-operating voltage,especially using air-stable aluminum as cathode,may be helpful for the devices to be used in commercially viable displays.     

High performance blue organic light-emitting devices fabricated by using the doped Alq3 in NPB hole transmistion layers

We have designed a new structure blue emission device with doped Alq3 of 3% in hole transmission layers of NPB. The CIE coordination of the devices is (0.17,0.19). The maximum electroluminescence efficiency is 4.1 cd/A at 11V, the brightness is 118.8 cd/m2 at 7 V, and the maximum brightness is 10770 cd/m2 at 13V.     

高效率磷光与荧光相结合的白色有机发光器件

制作了一种白色有机电致发光器件(WOLED)。将红光[Ir(piq)2(acac)]及绿光[Ir(ppy)3]磷光掺杂染料分别掺入到母体CBP中,在2种磷光发光层间插入蓝光材料DPVBi,引入电子传输能力强的BPhen作为电子注入层和空穴阻挡层,通过改变蓝光发光层的厚度,得到了高效率的WOLED,最大电流效率可达17.6cd/A,最大功率效率达13.7lm/W,最大亮度达27525cd/m2,当电压从4V变化到12V时,色坐标从(0.54,0.35)变化到(0.30,0.31),基本处于白光区。器件的特点在于DPVBi的存在阻挡了2种磷光材料间的能量转移,色度可以通过简单地调整DPVBi的厚度,避免使用稀有的蓝光磷光材料和与其相匹配的母体材料,同时又可以保持较高的发光效率。     

具有复合空穴传输层的高效低压有机电致发光器件

报道了用m-MTDATA掺杂NPB作复合空穴传输层(c-HTL)的高效率、低电压有机电致发光器件(OLED),器件的最高发光效率达到了5.3cd/A,比NPB作HTL的器件(3.4cd/A)提高了约50%.这是由于c-HTL具有较低的空穴迁移率,改善了发光层中两种载流子的平衡,从而提高了器件性能.进一步在ITO与c-H...