不同电子传输层的蓝光有机电致发光器件的性能研究

自从Tang等^[1]首次报道多层有机电致发光器件（OLED）以来,其在亮度和效率上有了质的飞跃,表明器件的结构对提高发光亮度和发光效率起着至关重要的作用,单层器件虽然具有制作简单的优点,但却存在明显缺点：（1）复合发光区靠近金属电极,该处缺陷很多,非辐射复合几率大,导致器件效率降低;（2）由于两种载流子注入不平衡,载流子的复合几率较低,因而影响器件的发光效率,要使发光层中具有高的载流子辐射复合效率,两种载流子的注入及传输能力应相当,否则传输快的一方就会直接穿过发光层到达对电极被猝灭,平衡电子和空穴的注入与传输可通过在电极和发光层之间加入载流子输运层或限制层制作多层器件的途径来实现,基于上述考虑,我们以PPCP为发光层（PPCP是一种荧光效率较高的蓝光材料^[2-4],对其进行深入研究尚未见有文献报道＿,设计了4种不同电子传输层（ETL)的三层 结构的OLED,为研究电子传输层对器件性能的影响,我们还制备了不含电子传输层的双层器件,结果表明,通过选择合适的ETL,OLED的发光亮度及发光效率会有很大程度的改善。     

小分子有机电致发光器件和材料的研究及应用

有机电致发光器件(OLED)是在电场作用下,以有机材料为活性发光层的器件.由于OLED具有亮度高、响应快、视角宽、工艺简单、可柔性等优点,在现代科学研究及技术应用中备受关注.其商业化应用,诸如平板显示(FPD)和固体照明(SSL)等,正在不断向前推进.本文综述了小分子OLED的各种器件结构和功能材料研究进展以及该领域存...     

半晶性有机半导体薄膜形态结构及对有机发光器件老化的影响

以NPB（N,N’-二苯基-N,N’-二（1-萘基）-1,1’-联苯-4,4’-二胺）为例,简要综述了本课题组近年来在发光有机半导体薄膜形态结构方面的研究进展．通过差热分析、偏光显微镜、透射电子显微镜、电子衍射、原子力显微镜表征,确认NPB是一类本征半晶性材料．一般的OLED器件采用的是非晶的NPB薄膜．基于等温结晶和表面诱导结晶实验确认,OLED器件可能存在两种热力学老化机制．对于采用非晶衬底的OLED器件,当NPB薄膜厚度小于临界厚度时器件可以稳定工作;对于采用多晶缓冲层衬底的OLED器件,由于表面诱导NPB结晶不存在临界厚度限制,器件容易结晶老化．     

有机、聚合物薄膜电致发光器件的研究进展

有机、聚合物薄膜电致发光器件是近年来国际上的一个研究热点。与无机材料相比, 有机材料具有更高的发光效率和更宽的发光颜色选择范围, 并且具有容易大面积成膜的优越性。本文介绍了有机、聚合物薄膜电致发光器件的结构和制备、发光机理以及有关材料的选择, 并对该研究领域的最新动态、器件的稳定性问题以及应用前景进行了讨论。     

基于Zn(Q-Ph)2与DCJTB非掺杂型OLED的制备及其电致发光性能研究

合成了有机发光材料2-苯基-8-羟基喹啉锌Zn(Q-Ph)2, 通过1H NMR, UV-Vis及MS等手段对配合物进行了结构表征. 利用该材料与高效的红光染料DCJTB复合制备出全新结构的非掺杂型OLED器件, 其结构为ITO/NPB/DCJTB/Zn(Q-Ph)2/AlQ3/Al. 将DCJTB超薄层的厚度调节到0—2.0 nm范围内, OLED器件的发光色调经历了黄光、红光和橙光的转变, 并且探讨了DCJTB厚度对OLED发光机理以及发光复合区域的影响. 当DCJTB的厚度为0.5 nm时, 获得了稳定的红光发射, 该器件在5.5 V电压下启亮, 在25 V外加电压下发光亮度达到420 cd/m2, 对应的电流密度为250 mA/cm2.     

利用三线态激子提高有机/高分子发光器件的量子效率

有机/高分子电致发光器件(O/PLED) 的发光效率远低于理论值,除器件结构有待优化之外,大部分三线态激子的能量没有得到利用是主要原因.近年来,利用三线态激子的发光来提高O/PLED的发光效率取得了积极的进展.本文从利用三线态激子的发光机制入手,综述了国内外在高效发光领域磷光材料利用的主要研究进展及发展方向。     

蓝光热激活延迟荧光分子设计策略概述

热激活延迟荧光（thermally activated delayed fluorescence,TADF）分子由于三重态上的激子可以通过反向系间窜越到单重态并辐射发出荧光，因此在有机发光二极管（organic lightemitting diode, OLED）中理论上可以实现100%的激子利用率。具有TADF特性的发光材料融合了第一代荧光材料和第二代磷光材料的优点，不仅可以实现100%的内量子效率，还有助于降低器件的材料成本，被誉为第三代OLED发光材料，并成为突破高效稳定蓝光OLED瓶颈的潜在解决方案。本文从发光机理出发，系统阐述了高效稳定蓝光TADF分子的设计策略，包括高荧光量子产率、短延迟荧光寿命、窄发射光谱半峰宽、显著的水平分子取向和良好的光电稳定性等。本文旨在为高性能蓝光TADF分子的开发提供理论支持。最后，总结了当前蓝光TADF材料存在的问题，并对其未来的发展前景进行了展望。     

有机电致发光器件的结构、发光机理及表面工程

简要介绍有机电致发光器件(OLED)的结构、发光机理、表面工程及检测、有机-无机电致发光材料的复合及制备技术。     

光致发光聚酰亚胺研究进展

聚酰亚胺是一类重要的高性能高分子材料,具有优异的热性能、机械性能、电学性能和尺寸稳定性等,同时具有良好的结构可设计性,已逐渐成为有机光电领域的研究热点.然而,传统聚酰亚胺材料一般不发光,文献中有关发光聚酰亚胺的研究并不多.同时,所报道的荧光量子产率普遍较低,极大地限制了其作为发光功能层在有机光电器件领域的应用.为了更好地了解聚酰亚胺发光的规律,拓展高性能聚酰亚胺材料在有机发光器件中的应用领域,本文介绍了聚酰亚胺光致发光的机理,综述了国内外有关光致发光聚酰亚胺的研究进展,总结了提高聚酰亚胺荧光量子产率的方法,并对未来高性能高效发光聚酰亚胺材料的研究方向做了展望.     

基于8-羟基喹啉及其衍生物的有机小分子电致发光材料

有机电致发光器件因驱动电压低、亮度和效率高等优点,已经成为最具潜力的平板显示技术。自以8-羟基喹啉铝为发光材料制备双层有机电致发光器件开始,科研人员在发光材料设计合成方面做了大量工作并取得了重大研究进展。在小分子荧光材料中,8-羟基喹啉及其衍生物为配体的有机金属配合物因合成方法简单、发光效率和亮度高、成膜性好等优点而被广泛应用。本文简述了有机电致发光器件的优点、结构及工作原理,重点介绍了基于8-羟基喹啉及其衍生物为配体的有机小分子电致发光材料的研究现状。从分子设计的角度出发,旨在总结8-羟基喹啉及其衍生物为配体的有机小分子电致发光材料对有机电致发光器件性能的影响,包括:以8-羟基喹啉为单一配体的有机金属配合物展示了良好的电子传输能力、亮度高且可作为基质材料等卓越的特性;通过对8-羟基喹啉的苯氧环或吡啶环进行修饰可以调节电致发光颜色;混合配体的使用可以增加玻璃化温度、改善薄膜形貌进而提高器件的效率和稳定性。最后,对该领域存在的问题和有机电致发光材料的应用前景作了评述。     

溶液加工型有机电致发光材料与器件研究进展

有机电致发光器件（OLEDs）在平板显示和固体照明领域有着广阔的应用前景,发展十分迅速,已实现了商业化．而可溶液加工的OLEDs采用喷墨打印、卷对卷印刷等低成本方式进行加工,在实现低成本、大面积显示及照明器件等方面具有巨大的应用潜力,引起了广泛关注．实现高效溶液加工型OLEDs的实用性需要在光电材料设计合成及器件制备方法上进一步深入研究．本文总结了发光材料与器件国家重点实验室可溶液加工型OLEDs材料及器件的研究进展．     

有机电致发光器件中载流子传输与复合的调控

在典型的多异质结器件ITO/NPB/CBP：Ir（ppy）3/Bphen/Alq3/LiF/Al的基础上,利用有机半导体掺杂技术,设计制备了单异质结-单发光层器件、单异质结-p-i-n结构器件、单异质结-双发光层器件及无异质结-混合主体结构器件,并对其光电性能进行了研究和比较.其中,单异质结-p-i-n结构器件的最大功率效率为32.1lm/W,是参考器件的3.1倍,寿命是参考器件的15倍.无异质结-混合主体结构器件的最大功率效率为37.2lm/W,是参考器件的3.5倍,其寿命是参考器件的46倍.研究结果表明,通过对载流子传输层和发光层的优化设计,构建电子、空穴传输平衡的载流子传输层和发光层,减少或取消异质结界面仍可以实现对载流子传输和复合的有效调控,从而使器件的发光效率和寿命同时得到提高.本研究将为高性能OLED的设计提供实验基础.     

A photochemical investigation into operational degradation of arylamines in organic light-emitting diodes

In this study, we investigated the operational degradation of 4,4′-bis(N-carbazolyl)biphenyl (CBP), an arylamine commonly used as phosphorescent host or hole transport material in organic light-emitting diodes (OLEDs), which have been subject to a recent surge in demand for use in the optical display market. In view of the important roles of organic components in the stability and lifetime of OLEDs, we initiated an investigation of the operational degradation of CBP in OLEDs in an effort to elucidate the degradation mechanism. Our experimental approach to this task is by performing photochemistry on CBP in solution, thereby avoiding actual operation of CBP-based OLEDs. Prior to the experiments, we calculated the C–N homolytic bond dissociation energy in CBP, and synthesized two CBP derivatives based on molecular engineering considerations. Furthermore, we performed TiO₂ photocatalytic decomposition of arylamines as a feasibility test for another operational degradation pathway. Based on both the photochemical and photocatalytic experiments, multiple operational degradation pathways of arylamines emerge.     

Synthesis of Anthracene Derivatives with Azaacene-Containing Iptycene Wings and the Utilization as a Dopant for Solution-Processed Organic Light-Emitting Diodes

Substituted acene derivatives are regarded as promising materials for organic electronic devices such as organic light-emitting diodes (OLEDs). In particular, anthracene derivatives are known to exhibit good fluorescence property, with the air stability and solubility in common organic solvents expected to give advantages for solution-processed device fabrication. In this study, a series of bistriisopropylsilyl(TIPS)ethynyl anthracene derivatives with azaacene-containing iptycene wings have been synthesized by using condensation reactions. Effects of size of azaacenes on optical properties and packing structures were investigated. UV/Vis absorption and fluorescence spectra indicate that the π-elongation of iptycene units has small effects on the overall π-system, which is also supported by electrochemical measurements. Secondly, single-crystal X-ray analysis implies that the molecules likely have interactions with the iptycene units of adjacent molecules, while the iptycene wings and TIPSethynyl groups can prevent the central anthracene unit from undesirable non-radiative energy loss. Finally, the most emissive derivative was used as a dopant for solution-processed OLEDs, showing obvious electroluminescence with a luminance of over 920 cd m⁻².     

吖啶衍生物的合成、表征、光致发光及电致发光性质研究

本文设计合成了一系列以吖啶为核的荧光小分子发光化合物（1～4）,通过在分子两侧引入不同的取代基来调节化合物的能级、载流子传输性质.对这些材料的光物理、电化学、热力学和能量转移性能进行了系统表征.结果表明这些材料具有高的发光效率、合理的能级结构和良好的主/客体能量转移特性.以这些材料为发光层的器件显示了优良的性能,电致发光器件的开启电压为2.4V,最高效率可达到13.3lm/W和11.8cd/A.     

聚合物热激活延迟荧光材料的分子设计与器件性能

聚合物热激活延迟荧光(TADF)材料应用于有机发光二极管(OLEDs)中以来,取得了飞速发展,迄今为止已经报道了多种不同分子结构及性能优异的聚合物TADF发光材料.它们具有不含重金属的化学结构、100%的理论内量子效率和易于通过溶液加工进行大面积制造的优势.本文从分子结构和发光颜色2个角度总结了不同结构TADF聚合物的研究进展,重点介绍了我们课题组在长链型TADF聚合物设计与OLEDs器件性能方面的研究工作,探究TADF聚合物颜色调控与效率提升的途径,论述了TADF聚合物存在的问题与未来发展.     

甲基修饰的咔唑/二苯砜基AIE-TADF蓝光材料及其OLED器件

以四甲基咔唑为电子给体(D)、 二苯砜为电子受体(A)构建了具有D-A-D结构的纯有机咔唑/二苯砜衍生物——9,9'-[磺酰基双(3,1-亚苯基)]双(1,3,6,8-四甲基-9H-咔唑)(TMe-mSOCz). 对所合成材料的光物理性能研究表明, TMe-mSOCz表现出明显的聚集诱导发射(AIE)和热激活延迟荧光(TADF), 延迟寿命和延迟荧光占比分别为2.26 μs和47.7%, 并具有良好的电化学稳定性和热稳定性. 基于TMe-mSOCz作为非掺杂发光层制备了有机发光二极管(OLED)器件, 其启亮电压(V_on)为3.5 V, 最大外量子效率为5.63%, 国际照明委员会(CIE)坐标为(0.18, 0.26). 在1000 cd/m²亮度下, 非掺杂器件的效率滚降非常小(7.1%), 色彩稳定性较好, 其具有窄的半峰宽(FWHM=72 nm). 研究结果表明, 在传统TADF分子给受体间引入甲基修饰有利于开发具有AIE特性与更高效的D-A-D型TADF分子, 这为基于AIE-TADF分子开发新型OLED器件提供了新途径.     

Thermal stability of organic electroluminescent devices fabricated using novel charge transporting materials

Novel hole and electron transporting materials have been synthesized to improve the thermal stability of organic electroluminescent (EL) devices. Molecular structures of such hole and electron transporting materials were designed based on triphenylamine (TPA) and oxadiazole (OXD) moieties, respectively. It has been found that the resulting materials have high glass transition temperatures (Tg) over 100°C and the vacuum-deposited thin films are significantly thermally stable. For the two-layer EL devices using the novel hole transporting materials and the typical emitting material, tris(8-quinolinolato) aluminum, the thermal stability has been clearly seen to depend on the Tg of the hole transporting material; excellent thermal stability was achieved. For the three-layer EL device using the novel electron transporting material, good emission efficiency and good stability were achieved. The electron transporting materials have been also applied to the polymeric system with polyvinylcarbazole matrix.     

On the stability of a variety of organic photovoltaic devices by IPCE and in situ IPCE analyses - the ISOS-3 inter-laboratory collaboration

This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPV) devices prepared by leading research laboratories. All devices have been shipped to and degraded at RIS?-DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work, we apply the Incident Photon-to-Electron Conversion Efficiency (IPCE) and the in situ IPCE techniques to determine the relation between solar cell performance and solar cell stability. Different ageing conditions were considered: accelerated full sun simulation, low level indoor fluorescent lighting and dark storage. The devices were also monitored under conditions of ambient and inert (N(2)) atmospheres, which allows for the identification of the solar cell materials more susceptible to degradation by ambient air (oxygen and moisture). The different OPVs configurations permitted the study of the intrinsic stability of the devices depending on: two different ITO-replacement alternatives, two different hole extraction layers (PEDOT:PSS and MoO(3)), and two different P3HT-based polymers. The response of un-encapsulated devices to ambient atmosphere offered insight into the importance of moisture in solar cell performance. Our results demonstrate that the IPCE and the in situ IPCE techniques are valuable analytical methods to understand device degradation and solar cell lifetime.     

High‐Performance Non‐doped OLEDs with Nearly 100 % Exciton Use and Negligible Efficiency Roll‐Off

Non‐doped organic light‐emitting diodes (OLEDs) possess merits of higher stability and easier fabrication than doped devices. However, luminescent materials with high exciton use are generally unsuitable for non‐doped OLEDs because of severe emission quenching and exciton annihilation in neat films. Herein, we wish to report a novel molecular design of integrating aggregation‐induced delayed fluorescence (AIDF) moiety within host materials to explore efficient luminogens for non‐doped OLEDs. By grafting 4‐(phenoxazin‐10‐yl)benzoyl to common host materials, we develop a series of new luminescent materials with prominent AIDF property. Their neat films fluoresce strongly and can fully harvest both singlet and triplet excitons with suppressed exciton annihilation. Non‐doped OLEDs of these AIDF luminogens exhibit excellent luminance (ca. 100000 cd m^?2), outstanding external quantum efficiencies (21.4–22.6 %), negligible efficiency roll‐off and improved operational stability. To the best of our knowledge, these are the most efficient non‐doped OLEDs reported so far. This convenient and versatile molecular design is of high significance for the advance of non‐doped OLEDs.