Synthesis of an aromatic amine derivative with novel double spirobifluorene core and its application as a hole transport material

A synthetic method to prepare a novel double spirobifluorene core structure was developed and a hole transport type exciton blocking material with the double spirobifluorene core was synthesized. A two step ring closing method was used to synthesize the double spirobifluorene core. The double spirobifluorene core based hole transport material showed high glass transition temperature due to rigid structure, and high quantum efficiency in green phosphorescent organic light emitting diodes because of efficient hole injection and triplet exciton blocking properties.     

Bright organic electroluminescent devices with double-layer cathode

Electroluminescent devices were fabricated using a diamine derivative and tris (8-quinolinolato) aluminum (III) complex as the hole transport layer and the emitting layer, respectively. The glass substrate/anode/hole transport layer/emitting layer/cathode cells structure was employed. The anode was indium-tin-oxide (ITO) transparent electrode, and the cathode was a double layer consisting of first layer of Mg or Li and the second layer of Ag. Intense bright green emission with luminance of 40400 cd/m² was achieved at 18-V with a current density of 330 mA/cm² for the cell with the Al complex doped with 1 mol.% of coumarin 6 and Li/Ag as the cathode     

Development of an exciplex type mixed host using a pyrrolocarbazole type material for extended lifetime in green phosphorescent organic light-emitting diodes

Lifetime improvement of green phosphorescent organic light-emitting didoes (PHOLEDs) by an exciplex type host was studied by mixing a hole transport type host and an electron transport type host. A pyrrolocarbazole type material was developed as the hole transport type host and a triazine type material was the electron transport type host. The exciplex type mixed host showed much longer lifetime and improved efficiency compared with each host material constituting the exciplex type mixed host. Hole and electron stability of the exciplex host was proposed as the key factor for the long lifetime of the green phosphorescent device.     

High quantum efficiency and color stability in white phosphorescent organic light-emitting diodes using carboline derivative as a host material

Highly efficient and color stable phosphorescent white organic light-emitting diodes were developed using a high triplet energy host material, 3,3′-bis(9H-pyrido[2,3-b]indol-9-yl)-1,1′-biphenyl (CbBPCb), derived from carboline. Two color phosphorescent white organic light-emitting diodes were fabricated by co-doping of blue and orange triplet emitters or double emitting layer structure of blue and orange emitting layers. High quantum efficiency above 20% and color stability were achieved in the white device by optimizing the doping concentration and emitting layer thickness.     

BCP的厚度对OLED性能的影响

设计了一种有机电致发光器件（OLED）结构：ITO／NPB（50nm）／BCP（x）／Alq3（50mm）／LiF（0．5mm）／Al（120nm）。在实验中改变BCP的厚度,调整电子和空穴的注入平衡,控制发光层（EML）。研究发现：当BCP的厚度为0nm时,器件为典型的双层OLED结构,光谱为绿色的Alq3特征光谱;当厚度为8nm或8nm以上时,发光区完全基于NPB层,器件为蓝色发光;当厚度在1nm到8nm时,NPB层和Alq3层对发光都有贡献,EL谱线包括蓝光发射和绿光发射。BCP层起到了调节载流子复合区域和改变器件发光颜色的作用,因此控制BCP的厚度可以改善器件的性能。     

Cyanocarbazole Derivatives for High‐Performance Electroluminescent Devices

3‐Cyano‐9‐diarylamino carbazoles have been synthesized. These new compounds emit in the blue to green region. Double‐layer electroluminescent devices using these compounds as the hole‐transport/emitting materials are highly efficient. Two of the compounds can be fabricated into single‐layer devices with good performance. Green‐ and blue‐emitting devices with good performance were also fabricated using one of the compounds as the hole‐injection layer.     

Correlation of doping concentration,charge transport of host,and lifetime of thermally activated delayed fluorescent devices

Origin of doping concentration dependence of lifetime of thermally activated delayed fluorescent (TADF) devices was examined using a TADF emitter doped in a hole transport type and a bipolar host material. Lifetime of the hole transport type host based TADF device was increased according to doping concentration of TADF emitter, while that of the bipolar host based TADF device was decreased according to doping concentration of TADF emitter. The doping concentration dependence of the lifetime could be correlated with recombination zone of the emitting layer. Broad recombination zone at high doping concentration in the hole transport type host and at low doping concentration in the bipolar host was proposed as the main contributor of the doping concentration dependence of the lifetime.     

Interlayer free hybrid white organic light-emitting diodes with red/blue phosphorescent emitters and a green thermally activated delayed fluorescent emitter

Two different hybrid white organic light-emitting diodes (WOLEDs) with red/blue phosphorescent emitters and a green thermally activated delayed fluorescent (TADF) emitter were designed to develop high efficiency hybrid WOLEDs. One hybrid WOLED (type I) had a device structure with a hybrid emitting layer of green TADF and red phosphorescent emitters stacked on a blue phosphorescent emitting layer and the other hybrid WOLED (type II) had a device architecture with the green TADF emitting layer stacked on a red and blue phosphorescent emitting layer. Efficient energy transfer from the green TADF emitter to the red phosphorescent emitter was observed and balanced white emission could be obtained by optimizing the device structure of the hybrid WOLEDs. A quantum efficiency of 16.2% with a color coordinate of (0.45,0.47) and a quantum efficiency of 18.0% with a color coordinate of (0.37,0.47) were achieved in the type I and type II hybrid WOLEDs, respectively.     

Inkjet deposition of a hole-transporting small molecule to realize a hybrid solution-evaporation green top-emitting OLED

The QUPD molecule has been deposited by inkjet printing as a hole-transport layer in top-emitting green OLEDs. A systematic study of the QUPD-based ink formulation has been done and different solvent mixtures have been investigated, in order to find the best composition (QUPD in toluene/IPA/anisole, 8/1/1 v/v/v) leading to the best film forming properties. Spin-coated PEDOT-PSS has been used as hole injecting layer. Subsequent layers have been deposited by vacuum sublimation. The resulting hybrid, solution-sublimation, OLEDs have been encapsulated by atomic layer deposition using Al₂O₃ material. In order to overcome the issue related to the thickness control of the organic layers deposited from solution, second order cavity length OLEDs have been fabricated by modifying the n-doped electron transport layer thickness. In that case, the relative OLED efficiency variation (10.5%) due to the thickness variation is far less compared to first order cavity length (34%) allowing a better reproducibility of the OLED fabrication. In the end, high efficiency (18 lm/W) green OLEDs of two different sizes, 0.44 cm² and 4 cm², have been fabricated, using an inkjet printed QUPD layer as hole transporting layer.     

Bright Blue Light—emitting Diodes Based on a Novel Fluorescent Dye Containing Heterocyclic Groups

Novel molecular material ,1-benzothiazoly-3-pheny1-pyrazoline (BTPP) was found to function as bright blue light emitting dye in organic electroluminescent device, and its optical and electric characteristics were investigated. This heterovyclic compound exhibited good characteristics of blue photoluminescence and electroluminescence,which had the emission peak at 450nm .The single layer light-emitting devices using BTPP as light -emitting material dispersed in poly(N-vinylcarbazole)(PVK) and double layer ones using PBD as hole block layer above the light-emitting layer were fabricated using conventional spin-casting and vaccum vapour deposition methods. The introduction of PBD has enhanced electron injection and luminance efficiency, compared with the single layer LEDs.     

Nanoprint lithography of gold nanopatterns on polyethylene terephthalate

Nano-order metal pattern printing on plastic substrates was established by using hard stamp nanoprint lithography (NPL). A spin-on-glass (SOG) material, which is almost the same as quartz in composition, was used as the material for the hard stamp. The SOG acted as a positive-tone electron beam (EB) resist. Nanopatterns were fabricated by using electron beam lithography (EBL), and a developed pattern of SOG was used as the hard stamp. Further, two types of release coating methods were utilized. One method used a conventional silan coupling agent and the other, a chromium layer. After comparing the results of the methods, we found that the chromium layer formed a smooth surface and therefore used this layer as the release layer. In addition, chromium was changed to Cr₂O₃ because of the exposure to atmospheric air. Gold was used as the transfer metal and was deposited on the hard stamp covered with the chromium release layer. This stamp was then placed in contact with a PET substrate at 80 °C for 30 min. A gap width of less than 30 nm of gold was transferred onto the PET substrate. This process is very simple, and yet, it makes it possible to obtain a very high resolution metal pattern transfer by using hard stamp NPL.     

Simple-structure organic light emitting diodes: Exploring the use of thermally activated delayed fluorescence host and guest materials

We investigate the dependence of the performance of non-doped blue light emitting devices with thermally activated delayed fluorescence (TADF) material bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS) emission layer on hole and electron transport layers as well as emission layer thickness and study the underlying device physics. On this basis, efficient green and orange devices using DMAC-DPS as host material and TADF material (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) or 2,3,5,6-tetrakis(3,6-diphenylcarbazol-9-yl)-1,4-dicyanobenzene (4CzTPN-Ph) as emitting dopant are reported. In addition, white devices using single DMAC-DPS: 4CzTPN-Ph emission layer show the maximum external quantum efficiency of 13.4%, maximum power efficiency of 38.3 lm W⁻¹ and current-insensitive Commission Internationale de I'Eclairage (CIE) coordinates of (0.29, 0.39). Compared to the approach of combining TADF host and fluorescent dopant, the present devices enable the utilization of all excitons for light emission and the adoption of broad dopant concentration without significantly affecting device efficiency, which is important for the realization of the desired colour purity for display applications, while maintaining the advantages of simple-structure and low-cost.     

Above 20% external quantum efficiency in green and white phosphorescent organic light-emitting diodes using an electron transport type green host material

Highly efficient green and white phosphorescent organic light emitting diodes were developed using a green phosphorescent host material based on phenyl substituted spirobifluorene. A high quantum efficiency of 25.3% was achieved in the green phosphorescent device and a high quantum efficiency of 21.6% was obtained in the white device with a stacked emitting structure of deep blue and red:green emitting layers.     

Improved Performance of White Phosphorescent Organic Light‐Emitting Diodes through a Mixed‐Host Structure

Highly efficient white phosphorescent organic light‐emitting diodes with a mixed‐host structure are developed and the device characteristics are studied. The introduction of a hole‐transport‐type host (N, N’‐dicarbazolyl‐3‐3‐benzen (mCP)) into an electron‐transport‐type host (m‐bis‐(triphenylsilyl)benzene (UGH3)) as a mixed‐host emissive layer effectively achieves higher current density and lower driving voltage. The peak external quantum and power efficiency with the mixed‐host structure improve up to 18.9% and 40.9 lm/W, respectively. Moreover, this mixed‐host structure device shows over 30% enhanced performance compared with a single‐host structure device at a luminance of 10,000 cd/m² without any change in the electroluminescence spectra.     

基于CBP的高效稳定绿色磷光OLED

使用真空蒸镀法分别制作了以TCTA和CBP做为主体材料的绿色磷光OLED器件,发现采用CBP为主体材料的器件比采用TCTA为主体材料的器件更稳定。之后在采用CBP作为主体材料的器件中分别掺杂了3%,6%,9%的蓝色客体磷光材料FIrpic,得出在掺杂浓度为3%时,即器件结构为ITO/HAT-CNTAPC/CBP:8%Ir (ppy)3:3%FIrpic/Tmpypb/Liq/Al时性能最佳。FIrpic掺杂比例为3%时得到最大功率效率和最大电流效率分别为54.3 lm/W和64.8 cd/A,最大亮度为51 940 cd/m2。研究表明Firpic的掺杂,在不改变绿色磷光OLED光谱性能的同时,有助于提高绿色磷光OLED的电光性能。     

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.     

CBP超薄层对有机电致磷光器件效率的影响

在空穴传输层(HTL)和发光层(EML)间插入4,4-N,N′-二咔唑基联苯(CBP)超薄层,制备了结构为ITO/NPB/CBP(xnm)/CBP:Ir(ppy)3/BCP/Alq3/LiF/Al有机电致磷光器件。与未插入CBP超薄层的器件相比,CBP超薄层的引入可以有效阻挡Ir(ppy)3的三线态能量通过Dexter能量转移到HTL的NPB中,减少无辐射能量损失,提高了器件发光效率。调整CBP薄层的厚度,当x为3nm时,器件的效率提高幅度最大,从x为0nm时的9.0cd/A提高到16.9cd/A。     

Binaphthyl‐Containing Green‐ and Red‐Emitting Molecules for Solution‐Processable Organic Light‐Emitting Diodes

Strong intermolecular interactions usually result in decreases in solubility and fluorescence efficiency of organic molecules. Therefore, amorphous materials are highly pursued when designing solution‐processable, electroluminescent organic molecules. In this paper, a non‐planar binaphthyl moiety is presented as a way of reducing intermolecular interactions and four binaphthyl‐containing molecules ( BNCM s): green‐emitting BBB and TBT as well as red‐emitting BTBTB and TBBBT , are designed and synthesized. The photophysical and electrochemical properties of the molecules are systematically investigated and it is found that TBT , TBBBT , and BTBTB solutions show high photoluminescence (PL) quantum efficiencies of 0.41, 0.54, and 0.48, respectively. Based on the good solubility and amorphous film‐forming ability of the synthesized BNCM s, double‐layer structured organic light‐emitting diodes (OLEDs) with BNCM s as emitting layer and poly(N‐vinylcarbazole) (PVK) or a blend of poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)benzidine] and PVK as hole‐transporting layer are fabricated by a simple solution spin‐coating procedure. Amongst those, the BTBTB based OLED, for example, reaches a high maximum luminance of 8315 cd · m⁻² and a maximum luminous efficiency of 1.95 cd · A⁻¹ at a low turn‐on voltage of 2.2 V. This is one of the best performances of a spin‐coated OLED reported so far. In addition, by doping the green and red BNCM s into a blue‐emitting host material poly(9,9‐dioctylfluorene‐2,7‐diyl) high performance white light‐emitting diodes with pure white light emission and a maximum luminance of 4000 cd · m⁻² are realized.     

Efficient low-molecule phosphorescent organic light-emitting diodes fabricated by wet-processing

We demonstrate high efficiency electrophosphorescence in organic light-emitting devices employing a phosphorescent dye doped into a low-molecule material. Methoxy-substituted 1,3,5-tris[4-(diphenylamino)phenyl]benzene (TDAPB) was selected as the host material for the phosphorescent dopant fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)₃], and organic films were fabricated by spin-coating. A peak external quantum efficiency of 8.2% (29 cd/A), luminous power efficiency of 17.3 lm/W, and luminance of 33,000 cd/m² were achieved at 9.4 V with a 90 nm-thick emitting layer. Emission from the host TDAPB material was not observed in the electroluminescence (EL) and photoluminescence (PL) spectra. The decrease in efficiencies at a high current is analyzed using the triplet–triplet annihilation model. The high performance for the simple device structure in this study is attributed to excellent film forming properties of the material and efficient energy transfer from the host to dopants.     

基于纳米氧化钛电子传输层的量子点发光二极管器件的制备与研究

为了获得高效而经济的光电器件,采用湿法旋涂技术制备量子点发光二极管器件( QLED),并对其光电特性进行了测试。此器件基于纳米二氧化钛( TiO2)的电子传输层,采用ITO玻璃作为阳极,Al为阴极,PEDOT为空穴注入层,TFB为空穴传输层,量子点( QD)作为发光层的结构。研究发现,QLED器件的开启电压为2.6 V,发光高度大于10 cd/m2。实验结果说明了TiO2可以作为获得高效QLED器件以及其他光电器件的一种有效途径。