蓝色磷光有机发光材料

有机发光二极管在信息显示和固体照明领域具有广阔的应用前景,二十多年来得到了广泛关注,取得了很大进展。但显示和照明必需的蓝色发光材料,特别是蓝色磷光材料是目前有机发光材料研究领域的瓶颈,其稳定性和效率亟待提高。本文总结了近年来蓝色磷光有机发光材料的研究进展,系统介绍了蓝色磷光染料和主体材料这两大类材料的分子设计思想和发展动态,以及它们在有机发光二极管中的应用,并对蓝色磷光有机发光材料未来的研究方向进行了展望。     

蓝色有机电致磷光主体材料

有机电致发光(OLEDs)因其具有驱动电压低、主动发光、亮度高、视角宽、响应快、耐冲击与震动等特点,在平板显示与照明领域有着广阔的应用前景。磷光有机电致发光二极管(PhOLEDs)由于能够同时利用三重态和单重态激子,内量子效率从理论上可达到100%,从而克服了传统荧光OLEDs只利用单重态激子时效率25%的限制,在过去的几十年里受到业内人士的极大关注。但要实现三重态磷光,通常需要将重金属原子与主体材料进行掺杂,而重金属配合物的磷光寿命相对较长,容易引起浓度猝灭和三重态-三重态湮灭,所以需要找到合适的主体材料与重金属的磷光发射体进行掺杂来减少上述因素的影响从而得到高性能的电致磷光器件。本文综述了近年来国内外蓝色有机电致磷光主体材料的研究状况,并对空穴传输型、电子传输型和双极传输型的蓝色磷光主体材料按照官能团的不同进行了分类总结和评述,并对其光物理性质、热学性质、电化学性质及器件性能等作了详细归纳比较,最后展望了蓝色有机电致磷光主体材料的前景和发展趋势。     

基于二苯甲酮框架的多功能有机发光材料

有机发光材料的光电性能与分子的化学结构、构象变化的灵活性以及分子间相互作用密切相关。从结构上看,二苯甲酮的羰基和苯环具有很高的可化学修饰性,本文从材料合成角度首先综述了近年来基于二苯甲酮框架的多功能有机发光材料的构建策略,主要包括多取代二苯甲酮、用杂原子作为桥连基团以及以C=C偶联和苯环为中心直接偶联等三种策略。已经基于此开发了多种多功能有机发光材料,主要包括荧光材料、贵金属磷光配合物的主体、热激活延迟荧光材料、聚集诱导发光材料和纯有机室温磷光材料等。最后,还展望了基于二苯甲酮框架的多功能有机发光材料未来的研究重点和发展前景。     

无间隔层结构的高效率荧光/磷光混合型白光有机发光二极管

采用磷光红光/荧光蓝光/磷光绿光无间隔层三发光层结构,制备出了高效率荧光/磷光混合型白光有机发光二极管(OLEDs),其中选取具有高荧光量子产率(PLQY)的荧光染料4P-NPD(双[N-(1-萘基)-N-苯基-氨基]四联苯)作为蓝光发射分子,以及常用的高效磷光染料Ir(MDQ)₂(acac)和Ir(ppy)₃(acac)分别作为红光和绿光的客体,通过混合和掺杂的方法制备了相应的发光层,实现了发光层中激子的有效利用和白光发射。 制备的白光器件最大电流效率和功率效率分别达到了27.1 cd/A和30.3 lm/W,当电压为6 V时,CIE色坐标为(0.33,0.41),显色指数CRI为70,色温CCT为5432 K。 在此基础上,设计制备了高色温的荧光/磷光混合型白光OLEDs,其色温(CCT)达到了7106 K。     

基于荧光与磷光复合的有机电致白光器件

白光有机电致发光器件(white organic light emitting diodes,WOLEDs)在显示和照明领域有着极大的应用前景,受到人们的广泛关注.基于荧光和磷光复合发光的WOLEDs结合了荧光器件与磷光器件的优点,提供了实现高效白光器件的新思路.本文按小分子和聚合物器件分类综述了近年来荧光磷光复合发光白光器件的研究进展,对器件结构、荧光磷光之间的能量传递与发光机理等方面进行了讨论,并对此类器件未来的研究方向进行了展望.     

高分子发光材料研究进展

高分子发光材料具有可溶液加工的特点,适于制备低成本、大面积发光器件,在平板显示和固体照明领域具有潜在的应用前景.近年来,高分子发光材料在发光机制、材料体系和器件性能等方面均取得了重要进展,各项性能得到了大幅度提升.本文从材料和器件角度,围绕高分子荧光材料、高分子磷光材料和高分子热活化延迟荧光材料的分子设计策略,总结和评述了高分子荧光材料的颜色调控和效率提升途径,高分子磷光材料的磷光掺杂剂、高分子主体、拓扑结构等因素对发光性能的影响规律,以及高分子热活化延迟荧光材料的设计原理和典型材料体系.同时,分析了高分子发光材料未来发展面临的机遇和挑战.     

有机小分子室温磷光材料的研究进展

室温磷光不仅能直观地反映磷光发光体的激发态跃迁过程,而且在光电、传感、生物成像和信息加密等领域具有广阔的应用前景.因此,近年来室温磷光材料的研究引起了人们越来越多的兴趣与关注,成为发光材料、尤其是有机发光功能材料领域的一个新的研究热点.本综述总结了近年来关于有机小分子室温磷光材料的研究进展,主要围绕基于氢键的室温磷光材料、含有卤素的室温磷光材料、基于给体-受体（D-A）结构的室温磷光材料和具有圆偏振发光（CPL）性质的有机小分子室温磷光材料展开介绍.     

荧光/磷光混合型白光有机发光二极管的研究

白光有机发光二极管（white organic light-emitting diodes,WOLEDs）在全色显示、固态照明以及背光源等领域有巨大的应用前景,其研究备受关注.其中,荧光/磷光混合型WOLEDs因兼具荧光材料的长寿命和磷光材料的高效率,被认为是目前最有希望实现照明应用的器件结构.荧光/磷光混合型WOLEDs最重要的问题是要解决荧光材料的单线态激子和磷光材料的三线态激子的协同发光.为了避免单线态激子和三线态激子的相互猝灭问题,必须设计有效的器件结构.本文以两种不同三线态能级的蓝光荧光材料为研究对象,介绍了不同高性能荧光/磷光混合型WOLEDs的结构设计与性能.研究表明,载流子传输平衡的高效结构设计和激子分布宽范围内的有效调控是实现高性能荧光/磷光混合型WOLEDs的关键.     

蓝色有机电致发光材料及器件的研究进展

有机电致发光器件因在全彩平板显示和固态照明领域中具有广阔的应用前景, 而受到人们的广泛关注。 时至今日, 与现有的红色和绿色有机电致发光材料和器件相比, 具有优越综合性能的蓝色有机电致发光材料和器件却始终匮乏。 相对而言, 蓝光材料具有较宽的能隙, 因而很难获得低电压、高效率和良好稳定性的深蓝光器件。 通常, 白色有机电致发光器件可以通过混合三基色或者两种颜色的方法获得。 但是无论哪种方法, 蓝光材料均是必不可少的。 另外, 还可以通过能量传递将蓝光转化为红光和绿光。 因此, 研发出具有优越综合性能的蓝光材料对有机电致发光器件的推广及应用十分关键。 本文综述了近年来蓝色荧光材料、蓝色磷光材料的研究进展以及蓝光材料在蓝色和白色有机电致发光器件中的应用, 并结合现有工作, 对蓝色有机电致发光材料的研究和应用前景进行展望。     

室温磷光凝胶研究进展

室温磷光(RTP)材料因其独特的发光性质和在光电、传感、生物成像及信息加密等领域广阔的应用前景吸引了研究者的兴趣。近年来,科学家探索了各种方法调控有机分子的室温磷光,并通过磷光分子结构设计以及磷光保护基质的构建成功构筑了长寿命和高量子效率的有机室温磷光材料。超分子凝胶作为诱导室温磷光的新基质,具有三维网络结构、热可逆性质及刺激响应性等优势而引起关注。本综述围绕无金属室温磷光凝胶材料和含金属室温磷光凝胶材料,总结了近年来关于室温磷光凝胶材料的研究现状,并在此基础上,简要展望了室温磷光凝胶材料研究的发展趋势。     

High Performance Thermally Activated Delayed Fluorescence Sensitized Organic Light‐Emitting Diodes

Recently, organic light‐emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) materials have aroused huge attention in both academia and industry. Compared with fluorescent and phosphorescent materials, TADF materials can theoretically capture 100 % excitons without incorporating noble metals, making them effective emitters and hosts for OLEDs simultaneously. Here, in this review, our recent works on mechanisms and materials of high performance TADF‐sensitized phosphorescent (TSP) OLEDs, TADF‐sensitized fluorescent (TSF) OLEDs and TADF‐sensitized TADF (TST) OLEDs are summarized. Finally, we propose the outlook for the further development and application of TADF‐sensitized OLEDs.     

稠杂环化合物在红色磷光铱配合物中的应用

在过去的几十年里, 有机发光二极管(OLED)由于潜在的优势, 在全彩显示领域引起了高度重视. 电致磷光材料因其优异的发光性能, 引起了人们广泛关注. 对于实际应用的平板显示器, 蓝、绿、红三基色是必不可少的. 相对于高效的绿光材料, 红光磷光材料仍然存在色纯度差、效率低和亮度不足等问题, 因此设计合适的红光材料成为具有挑战性的问题. 稠杂环化合物因发光量子效率高、发光颜色可调、平衡电荷注入及迁移等优越性能而广泛应用于红色磷光铱配合物. 本文综述了近几年稠杂环化合物在小分子、树枝状及高分子红色磷光铱配合物中的应用, 阐述了铱配合物分子结构对材料光电性质及器件性能的影响, 最后展望了稠杂环化合物在红光磷光材料中的应用前景.     

Phosphorescent Pt(II) Emitters for OLEDs: From Triarylboron‐Functionalized Bidentate Complexes to Compounds with Macrocyclic Chelating Ligands

The development of organic light‐emitting diodes (OLEDs) has attracted enormous research efforts from both academia and industry in the past decades and tremendous progress has been made. However, the low operation lifetime of the blue phosphorescent OLEDs remains as one of the greatest bottlenecks limiting further applications of OLEDs. To address this problem, design and synthesis of triplet emitters with high phosphorescence quantum yield (Φ_P) and adequate thermal, chemical, electrical and ultraviolet (UV) stabilities are vital. This review summarizes the progress we made on the development of efficient and robust phosphorescent emitters based on cyclometalated Pt(II) compounds, particularly the ones with blue emission, starting from complexes with triarylboron‐functionalized bidentate ligand to molecules incorporating tetradentate and macrocyclic ligands, with emphasis on their structure‐property relationships.     

Benzimidazobenzothiazole‐Based Bipolar Hosts to Harvest Nearly All of the Excitons from Blue Delayed Fluorescence and Phosphorescent Organic Light‐Emitting Diodes

Much effort has been devoted to developing highly efficient organic light‐emitting diodes (OLEDs) that function through phosphorescence or thermally activated delayed fluorescence (TADF). However, efficient host materials for blue TADF and phosphorescent guest emitters are limited because of their requirement of high triplet energy levels. Herein, we report the rigid acceptor unit benzimidazobenzothiazole (BID‐BT), which is suitable for use in bipolar hosts in blue OLEDs. The designed host materials, based on BID‐BT, possess high triplet energy and bipolar carrier transport ability. Both blue TADF and phosphorescent OLEDs containing BID‐BT‐based derivatives exhibit external quantum efficiencies as high as 20 %, indicating that these hosts allow efficient triplet exciton confinement appropriate for blue TADF and phosphorescent guest emitters.     

Progress in small-molecule luminescent materials for organic light-emitting diodes

Organic light-emitting diodes(OLEDs) have been extensively studied since the first efficient device based on small molecular luminescent materials was reported by Tang. Organic electroluminescent material, one of the centerpieces of OLEDs, has been the focus of studies by many material scientists. To obtain high luminosity and to keep material costs low, a few remarkable design concepts have been developed. Aggregation-induced emission(AIE) materials were invented to overcome the common fluorescence-quenching problem, and cross-dipole stacking of fluorescent molecules was shown to be an effective method to get high solid-state luminescence. To exceed the limit of internal quantum efficiency of conventional fluorescent materials, phosphorescent materials were successfully applied in highly efficient electroluminescent devices. Most recently, delayed fluorescent materials via reverse-intersystem crossing(RISC) from triplet to singlet and the "hot exciton" materials based on hybridized local and charge-transfer(HLCT) states were developed to be a new generation of low-cost luminescent materials as efficient as phosphorescent materials. In terms of the device-fabrication process, solution-processible small molecular luminescent materials possess the advantages of high purity(vs. polymers) and low procession cost(vs. vacuum deposition), which are garnering them increasing attention. Herein, we review the progress of the development of small-molecule luminescent materials with different design concepts and features, and also briefly examine future development tendencies of luminescent materials.     

Diversity of Luminescent Metal Complexes in OLEDs: Beyond Traditional Precious Metals

Organic light-emitting diodes (OLED) have attracted increasing attention due to their excellent properties, such as self-luminosity, high color gamut and flexibility, and potential applications in display, wearable devices and lighting. The emitters are the most important composition in OLEDs, mainly classified into fluorescent compounds (first generation), metal phosphorescent complexes (second generation), and thermally activated delayed fluorescence (TADF) materials (third generation). In this review, we summarize the advances of novel emitters of organic metal complexes in the last decade, focusing on coinage metals (Cu, Ag, and Au) and non-precious metals (Al, Zn, W, and alkali metal). Also, the design strategy of d¹⁰ and Au(III) complexes was discussed. We aim to provide guidance for exploring efficient metal complexes beyond traditional phosphorescent complexes.     

Design and Development of Highly Efficient Light‐Emitting Layers in OLEDs with Dimesitylboranes: An Updated Review

With excellent luminescent properties and transport properties, triarylborane compounds containing two mesitylenes (Mes) have gained much attention for their application in OLEDs as light‐emitting layers. This study serves as an updated review summarizing recent developments in the design of fluorescent chromophores and phosphorescent host materials for OLEDs comprising small molecular compounds of dimesitylborane (BMes₂) as luminescent layers, with attention to the performance of different light‐emitting devices. Problems that need to be solved in the research and application of BMes₂ in OLEDs are presented and the application prospects of such materials are suggested.     

Molecular Design Tactics for Highly Efficient Thermally Activated Delayed Fluorescence Emitters for Organic Light Emitting Diodes

Recently, pure organic thermally activated delayed fluorescence (TADF) emitters have attracted considerable interest from the scientific community in the field of organic light emitting diodes (OLEDs) as they can theoretically realize 100 % of the internal quantum efficiency by exploiting both the singlet and triplet excitons via the reverse intersystem crossing enabled by small singlet‐triplet energy splitting. Currently, the external quantum efficiency of the TADF emitters is reaching the level of phosphorescent emitters. Therefore, the TADF approach is considered as a potential alternative to the low efficiency conventional fluorescent and expensive phosphorescent emitters. In this account, we summarized our recent development of blue and green TADF molecular designs to improve the device performances of the TADF devices.     

Investigation of FIrpic in PhOLEDs via LC/MS technique

The commercial breakthrough of phosphorescent organic white light sources is presently hampered due to the unavailability of a stable blue phosphorescent emitter material. Moreover, only few analytical investigations have been made regarding the chemical degradation of the phosphorescent emitter materials during the processing or the operation of the devices. Organic light emitting devices (OLEDs) containing phosphorescent metal complexes with iridium as central ion were investigated. Special attention was paid to the chemical degradation of the material. The devices were analyzed by means of high performance liquid chromatography coupled with mass spectrometry (HPLC/MS). Electron spray ionization (ESI) was employed as ionization source. Isomerization phenomena of the blue-green emitting heteroleptic iridium complex FIrpic could be observed after the device manufacture and after operation. These findings could give hints on the mechanisms that influence the lifetime of PhOLEDs based on FIrpic or similar blue emitters.