Fabrication of a white organic light-emitting device with single liq：rubrence luminescent layer

Akind of white OLED with single luminescent layer was designed, in which rubrene was doped in Liq. The structure of the devices is ITO/PVK：TPD/Liq： Rubrene/Alq3/Al. The brightness of the devices comes to 3120 cd/m^2（at a driving voltage of 25 V）, the CIE coordinates of the typical devices is （0.308,0.347）, and the coordinates is very close to the white equi-energy point. The emitting and luminescent characteristics of the devices were discussed.     

Effects of transparent MPTMS/Ag/MoO3 structure as anode on the performance of green organic light-emitting diodes

A transparent 3-mercaptopropyl trimethoxysilane (MPTMS)/Ag/MoO3 composite anode is introduced to fabricate green organic light-emitting diodes (OLEDs). Effects of the composite anode on brightness and operating voltage of OLEDs are researched. By optimizing the thickness of each layer of the MPTMS/Ag/MoO3 structure, the transmittance of MPTMS/Ag (8 nm)/MoO3 (30 nm) reaches over 75% at about 520 nm. The sheet resistance is 3.78 Ω/□, corresponding to this MPTMS/Ag (8 nm)/MoO3 (30 nm) structure. For the OLEDs with the optimized anode, the maximum electroluminescence (EL) current efficiency reaches 4.5 cd/A, and the maximum brightness is 37 036 cd/m2. Moreover, the OLEDs with the optimized anode exhibit a very low operating voltage (2.6 V) for obtaining brightness of 100 cd/m2. We consider that the improved device performance is mainly attributed to the enhanced hole injection resulting from the reduced hole injection barrier height. Our results indicate that employing the MPTMS/Ag/MoO3 as a composite anode can be a simple and promising technique in the fabrication of low-operating voltage and high-brightness OLEDs.     

Effect of BCP ultrathin layer on the performance of organic light-emitting devices

Based on conventional double layer device, triple layer organic light-emitting diodes （OLEDs） with two heterostructures of indium-tin oxide （ITO）/N,N＇-diphenyl-N,N＇-bis（1-naphthyl）（1,1 ＇-biphenyl）-4,4＇-diamine（NPB）/2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline （BCP）/8-Hydroxyquinoline aluminum （Alq3）/Mg：Ag USing vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electroluminescence （EL） spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.     

Organic light-emitting devices based on new rare earth complex Tb（p-CIBA）3phen

A new rare earth complex Tb（p-CIBA）3phen was synthesized and introduced into organic tight emitting devices （OLEDs） as emitting material. The Tb（p-CIBA）3phen was doped into PVK to improve the filmforming and hole-transporting property. Two kinds of devices were fabricated. The device structure is as the following. Single-layer device： ITO/PVK： Tb （p-CIBA） 3 phen /LiF/Al; double-layer device： ITO/PVK： Tb（p-CIBA）3phen/AIQ/LiF/AI. The performances of both devices were investigated carefully. We found that the emission of PVK was completely restrained,and only the green emission was observed from the electroluminescence. The full width at half maximum （FWHM） was less than 10 nm. The highest EL brighthess of the single-layer device is 25.4 cd/cm^2 at a fixed bias of 18 V,and the highest EL brightness of the double-layer device reaches 234.8 cd/cm^2 at a voltage of 20 V.     

Temperature characteristics of near infrared SPR sensors with Kretschmann configuration

An organic light-emitting diode(OLED) device with high efficiency and brightness is fabricated by inserting CuO_x/Cu dual inorganic buffer layers between indium-tin-oxide(ITO) and hole-transport layer(HTL). The CuO_x/Cu buffer layer limits the operating current density obviously, while the brightness and efficiency are both enhanced greatly. The highest brightness of the optimized device is achieved to be 14 000 cd/m~2 at current efficiency of 3cd/A and bias voltage of 15 V, which is about 50% higher than that of the compared device without CuO_x/Cu buffer layer. The highest efficiency is achieved to be 5.9 cd/A at 11.6V with 3400 cd/m~2, which is almost twice as high as that of the compared device.     

空穴传输层厚度对有机发光二极管性能的影响

采用聚乙烯基咔唑(PVK)作为空穴传输层,8-羟基喹啉铝(Alq3)作为发光层,制备了结构为ITO/PVK/Alq3/Mg∶Ag/Al的有机发光二极管(OLED),通过测试器件的电流-电压-发光亮度特性,研究了空穴传输层厚度对OLED器件性能的影响,优化了器件功能层的厚度匹配.实验结果表明,OLED的光电性能与空穴传输层的厚度密切相关,空穴传输层厚度为15nm时,OLED器件具有最低的启亮电压,最高的发光亮度和最大的发光效率.     

超微OLED的制备及其光电特性的研究

为了实现高亮度有机电致发光器件(OLED)及其尺寸的微型化,采用接触式光刻技术,通过真空热蒸镀制备了具有不同掩膜版结构的OLED。器件的结构为玻璃衬底/ITO/LiF/空穴传输层(HTL,NPD)/发光层(EML,0.5-0.6vol%Rubrene:Alq3)/电子传输层(ETL,Alq3)/阴极,其中LiF作为绝缘层。分别制得发光面积为45μm×2mm的微细器件和直径为44μm的微小器件。实验研究了其光电特性,结果表明,4.5μm×2.0mm微细器件的最大电流密度为7A/cm2,为44μm微小器件的最大电流密度为40A/cm2。     

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.     

Effect of BCP ultrathin layer on the performance of organic light-emitting devices

Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (BCP)/ 8-Hydroxyquinoline aluminum (Alq3)/Mg:Ag using vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electrolumines- cence (EL) spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.     

Improved current efficiency in organic light-emitting devices with a hole blocking layer

A hole-blocking layer (HBL) of 4,7-diphenyl-1,10-phenanthroline (BPhen) is incorporated between the emitting layer (EML) and the electron transport layer (ETL) for a tris-(8-hydroxyqunoline)aluminum based organic light-emitting device (OLED). Such a structure helps to reduce the hole-leakage to the cathode, resulting in an improved current effi-ciency. The BPhen improves the balance of hole and electron injections. The current efficiency is improved compared with that of the device without the blocking layer. The highest luminous efficiency of the device with 6 nm BPhen acting as a blocking layer is 3.44 cd/A at 8 V, which is improved by nearly 1.5 times as compared with that of the de-vice without it.     

Influence of electrode characteristics on the performance of organic light-emitting devices

Indium-tin oxide (ITO) substrates were treated by oxygen plasma for organic light-emitting devices (OLEDs). Using the ITO substrates aged for various times as hole-injecting electrodes, the double-layered OLEDs were fabricated by the vacuum sublimation technique, and the aging effect of treated ITO anodes on the performance of OLEDs was studied with respect to the electroluminescence efficiency, brightness and driving voltage. Experimental results reveal that the luminescent and electrical characteristics of the OLEDs are strongly dependent on the properties of the ITO anodes, and the ITO anodes aged for various times result in significant differences in device performance, which become worse with the increment of the aging time. The measurements of X-ray photoelectron spectroscopy (XPS) and surface energy show that carbon concentration increases, oxygen concentration reduces and surface energy decreases, and thereby the improved surface properties of ITO tend to decay, as the aging time increases. It indicates that the device performance of the OLEDs is closely related to the surface characteristics of the ITO anodes.     

Cadmium-free quantum dots based violet light-emitting diodes: High-efficiency and brightness via optimization of organic hole transport layers

Bright and efficient violet quantum dot (QD) based light-emitting diodes (QD-LEDs) with heavy-metal-free ZnSe/ZnS have been demonstrated by choosing different hole transport layers, including poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB), and poly-N-vinylcarbazole (PVK). Violet QD-LEDs with maximum luminance of about 930 cd/m², the maximum current efficiency of 0.18 cd/A, and the peak EQE of 1.02% when poly-TPD was used as HTL. Higher brightness and low turn-on voltage (3.8 V) violet QD-LEDs could be fabricated when TFB was used as hole transport material. Although the maximum luminance could reach up to 2691 cd/m², the devices exhibited only low current efficiency (∼0.51 cd/A) and EQE (∼2.88%). If PVK is used as hole transport material, highly efficient violet QD-LEDs can be fabricated with lower maximum luminance and higher turn-on voltages compared with counterpart using TFB. Therefore, TFB and PVK mixture in a certain proportion has been used as HTL, turn-on voltage, brightness, and efficiency all have been improved greatly. The QD-LEDs is fabricated with 7.39% of EQE and 2856 cd/m² of maximum brightness with narrow FWHM less than 21 nm. These results represent significant improvements in the performance of heavy-metal-free violet QD-LEDs in terms of efficiency, brightness, and color purity.     

具有新型电子传输层的有机薄膜电致发光器件

将8-hydroxy-quinolinato lithium(Liq)掺入4'7-diphyenyl-1,10-phenanthroline(BPhen)作为n型电子传输层(ETL),将tetrafluro-tetracyano-quinodimethane(F4-TCNQ)掺入4,4',4"-tris(3-methylphenylphenylamono)triphenylamine(m-MTDATA)作为p型空穴传输层(HTL),制作了p-i-n结构有机电致发光器件.为了检验传输层传导率的改善情况,制备了一系列单一空穴器件和单一电子器件.在引入BPhen:33wt% Liq作为ETL后,x% F4-TCNQ:m-MTDATA作为HTL后,器件的电流和功率效率明显改善.与控制器件(未掺杂)相比,性能最佳的掺杂器件的电流及功率效率分别提高了51%和89%,电压下降了29%.这是由于传输层传导能力的提高使得载流子在发光区域达到有效平衡.     

具有新型电子传输层的有机薄膜电致发光器件

将8-hydroxy-quinolinato lithium(Liq)掺入4'7-diphyenyl-1,10-phenanthroline(BPhen)作为n型电子传输层(ETL),将tetrafluro-tetracyano-quinodimethane(F4-TCNQ)掺入4,4',4"-tris(3-methylphenylphenylamono)triphenylamine(m-MTDATA)作为p型空穴传输层(HTL),制作了p-i-n结构有机电致发光器件.为了检验传输层传导率的改善情况,制备了一系列单一空穴器件和单一电子器件.在引入BPhen:33wt% Liq作为ETL后,x% F4-TCNQ:m-MTDATA作为HTL后,器件的电流和功率效率明显改善.与控制器件(未掺杂)相比,性能最佳的掺杂器件的电流及功率效率分别提高了51%和89%,电压下降了29%.这是由于传输层传导能力的提高使得载流子在发光区域达到有效平衡.     

Optimization of carrier transport layer: A simple but effective approach toward achieving high efficiency all-solution processed InP quantum dot light emitting diodes

High performance quantum dot light emitting diodes (QD-LED) are being considered as a next-generation technology for energy efficient solid-state lighting and displays. In recent years, cadmium (Cd)-based QLEDs have made great progress in performance, which is close to commercial applications. However, the performance of environmentally friendly Cd-free QD-LED still needs to be improved. In this letter, using InP/ZnS quantum dots (QDs), an environmentally friendly red QDs material, as the light emitting layer, low-cost all-solution processed red InP/ZnS QD-LED are fabricated. The optimized device with a hybrid multilayered structure employing an organic double hole transport layer (HTL) with doping small molecules (TFB/PVK:TAPC) and an inorganic ZnMgO nanoparticles (NPs) electron transport layer (ETL), here TFB, PVK and TAPC represent poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’-(N-(p-butylphenyl))-diphenylamine)], poly (9-vinlycarbazole) and 1,1-bis [4-[N,N′-di (p-tolyl)amino]phenyl]-cyclohexane, respectively. The best device exhibits a peak current efficiency (CE) of 7.58 cd A⁻¹, which is 2.4 times higher than the control device using PVK (HTL) and ZnO (ETL). At the same time, turn-on voltage dropped from 2.8 V (control devices) to 2.4 V. These superb QD-LED performances originate not only from the improved hole injection by the introduction of a double hole layer and the reduced the quenching of excitons by using ZnMgO NPs ETL but also from increasing the hole mobility with doping of small molecule materials in PVK to balance the carrier transportation. This work provides a simple and feasible idea with optimization the carrier transport for realizing high-efficiency QD-LED devices.     

LiF层对ITD/Alq~3/LiF∶Al器件性能的影响

分别制备了4种有机电致发光器件(OLEDs):ITO/Alq3/Al;ITO/Alq3/LiF(1.0nm):Al;ITO/Alq3/LiF(1.5nm)∶Al;ITO/Alq3/LiF∶(2.0nm)Al。研究了LiF的引入对金属电极与发光层界面的影响以及各种不同的界面态对器件发光性能的影响。研究结果表明:适当的LiF厚度的引入不仅可以改善器件的界面特性,而且可以提高器件的发光亮度及发光效率。     

Optoelectrical characteristics of organic light-emitting devices fabricated with different cathodes

Organic light-emitting devices (OLEDs) with various cathode structures were prepared on indium tin oxide (ITO) substrates by vacuum sublimation technique, and the effects of the device cathodes on the electroluminescence (EL) characteristics of OLEDs were studied in terms of the luminance, efficiency, driving voltage and threshold voltage. The results demonstrate that the optical and electrical performance of OLEDs depend on the properties of the devices' cathodes and the characteristics of the cathode–organic interface and the organic–organic interface. The optoelectrical performance of a device with composite cathodes is better than that of the devices with metal alloy and pure metal cathodes. The improvement in the device performance can be attributed to a more efficient electron injection at the cathode–organic interface, a better balanced hole and electron recombination in the light-emitting layer and fewer accumulated charges near the organic–organic interface.     

量子点发光器件的制备与仿真分析

为研究量子点发光器件结构与性能的关系,制备了以CdSe/ZnS量子点作为发光层、poly-TPD作为空穴传输层,Alq3作为电子传输层的量子点发光二极管,对器件结构及性能参数进行了表征,结果显示器件具有开启电压低、色纯度高等特点.结合测试数据,对量子点发光二极管进行了器件结构建模,利用隧穿模型及空间电荷限制电流模型对实验结果进行了分析,研究了器件中载流子的注入与传输机理.器件测试与仿真结果表明:各功能层厚度会影响载流子在量子点层的注入平衡,同时器件中载流子的注入与传输存在一转变电压,当外加电压低于转变电压时,器件中载流子的注入主要符合隧穿模型;当外加电压高于转变电压时,器件中载流子的注入主要符合空间电荷限制电流模型.研究结果验证了器件结构建模的合理性,可以利用仿真的方法进行器件结构优化并确定相关参数,这对器件性能的提高具有指导意义.     

量子点电致发光器件发光层能级变化与驱动电压的关系研究

以量子点电致发光器件(QLED)中能级分布和载流子浓度的关系为理论基础,研究了QLED发光层能级变化与驱动电压的关系,建立了数学模型.以CdSe/ZnS核壳结构量子点为发光层,计算了器件正常发光时的阈值电压,分析了电流密度与量子点中电子准费米能级与空穴准费米能级之差的关系.结果表明,当驱动电压大于9.8V时,CdSe/ZnS中电子的准费米能级与空穴的准费米能级之差大于1.03 eV,量子点电致发光器件正常发光;理论模型证实由于电子在发光层与电子传输层界面的大量积聚,导致淬灭发生,降低发光效率.