【作者】 江志雄；

【导师】 彭俊彪；

【作者基本信息】 华南理工大学 ， 材料物理与化学， 2014， 博士

【摘要】 白色有机发光二极管（WOLED）由于在显示和照明领域的潜在应用价值，以及简单的制备工艺，丰富的材料体系，吸引了科学界以及工业界的广泛关注。但是，目前所有商业化的产品都是基于小分子材料，以真空蒸镀工艺实现的，这种工艺的缺点在于前期设备投资大，材料浪费严重，而且成品率低，难以实现大面积等。而基于溶液加工工艺（例如喷墨打印、旋涂、提拉等）的WOLED恰好可以弥补真空蒸镀工艺的不足。然而大部分情况下，溶液加工工艺主要集中在有机功能层，想要真正摆脱真空蒸镀设备的束缚，就必须考虑金属阴极的溶液制备工艺。另外，虽然磷光材料的内量子效率可以达到100%，但是磷光材料的稳定性仍然是其向前发展过程中最大的绊脚石，因此要想获得稳定高效的器件性能，荧光材料体系的开发依然是众多科学家们努力的方向。为此，本论文的主要研究内容是基于溶液加工工艺，通过对荧光材料体系的开发以及器件结构的优化，制备高效的WOLED器件，探索全溶液加工制备PLED器件的工艺，研究能够实现―卷对卷‖生产方式的柔性有机发光二极管器件ITO阳极的图案化工艺，以及WOLED的应用：设计与制备大面积白光板等。我们重点研究了基于小分子材料的溶液加工工艺制备高效荧光白光器件。以第零代树枝状小分子蓝色荧光材料(G0)为主体，掺杂黄色小分子荧光材料（CN-DPASDB），在较低的掺杂浓度下，实现不完全的能量转移态，利用蓝色-黄色二元互补获得白光发射。由于主体材料G0是一种空穴传输占主导的材料，因此为了获得更加平衡的载流子复合，我们通过优化器件结构，一方面压制空穴的注入，另一方面增加电子的注入，最终获得了最大电流效率、功率效率和亮度分别为17.0cdA-1,15.6lm W-1和2.24×104cd m-2，其CIE坐标为(0.32,0.37)，CRI为64，外量子效率达6.45%。这一性能为目前文献报道中，基于溶液加工型小分子荧光白色有机发光二极管的最高性能。为了摆脱真空蒸镀设备的束缚，通过结合多功能缓冲层和喷墨打印阴极的制备工艺，我们实现了全溶液法制备PLED器件。由于银胶溶液具有非常强的侵蚀能力，为了阻挡银胶的侵蚀，同时实现有效的电子注入，我们引入了阴极缓冲层。阴极缓冲层位于印刷阴极和发光层之间，用水醇溶性共轭聚合物PFNR2与可交联固化的环氧树脂粘合剂共混而成，交联后的阴极缓冲层能够有效的阻挡银胶溶剂的侵蚀，同时保证有效的电子注入，并能与阴极墨水保持适当的亲和力。全溶液法的应用，为有机发光二极管彻底摆脱蒸镀系统的束缚迈出了重要的一步，大大降低了有机发光二极管的生产成本。为了实现―卷对卷‖的生产方式，必须使用柔性基底。OLED的溶液加工工艺与柔性基底与生俱来的契合，使得OLED在未来可实现穿戴式的梦幻显示屏。在柔性有机发光二极管（FOLED）的研究中，我们碰到了许多难题，其中第一个必须解决的难题就是柔性基底ITO图案化。由于ITO导电阳极材料本身的脆性，在刻蚀过程中，或者器件制备过程中，容易引起ITO被撕裂，而导致器件漏电流增大，性能下降。特别地，传统刻蚀方法步骤繁多，热处理温度较高，使得柔性基底ITO更易被刻花。因此，本论文中我们发明了一种新型的ITO薄膜刻蚀方法，该方法步骤简单，只需经过低温热处理即可完成刻蚀，特别适合柔性基底，解决了传统刻蚀方法应用于柔性基底的ITO图案化中遇到的难题：ITO易被刻花导致器件出现短路和断路。为了验证新型刻蚀方法的效果，在本论文的第五章中分析并对比了不同ITO刻蚀方法制备的FOLED器件J-V-L和LE-J曲线。由于新的刻蚀方法制备的ITO薄膜表面平整，无毛刺，无针孔，且操作简单，获得了接近玻璃基底的器件性能。基于小尺寸器件上的成功，我们进而设计了发光面积为1英寸的柔性ITO刻蚀图案，并成功制备出了基于溶液加工工艺的红光、绿光以及白光大面积FOLED器件。最后，对于WOLED的应用，在周军红博士论文[1]的基础上，进一步改善大面积WOLED背光板的器件性能，一方面，通过调整发光区域内部金属线的布局来提高背光板器件的电流利用率；另一方面，我们采用溶剂处理的工艺，在蒸镀金属阴极之前，对背光板的发光层进行甲醇或乙醇处理，减小有机层与金属界面的表面陷阱，有效的提高了器件的发光性能，最终成功制备出了发光均匀的4英寸溶液加工型WOLED背光板。更多还原

【Abstract】 Due to the potential applications in the field of display and solid-state-lighting, as well assimple preparation technology, and a wealth of material system, white organic light-emittingdiodes (WOLED) has attracted extensive attention not only in the scientific community butalso industry. However, at present, all commercialized OLED products are based on smallmolecular material by vacuum vapor deposition process. The disadvantage of this kind oftechnology is the huge capital for equipment investment, serious waste of materials, very lowyield, and difficult to achieve large area. While solution processing (e.g.,inkjet printing, spincoating, and dip coating, etc.) could just compensate for the lacks of vacuum depositionprocess. In most cases, however, the solution process technology is focused on organicfunction layers. If we want to get rid of the shackles of vacuum deposition equipmet, thetechnology of solution process metal cathode has to be considered. In addition, although theinternal quantum efficiency of phosphorescent material can reach100%, the stability is still astumbling block to their development. Therefore, in order to obtain stable and efficientdevices, many scientists still focus on developing of fluorescent material system. For thisreason, the main text of this paper is based on the solution process fluorescent materials,through optimizing the device structure, the highest efficient WOLED device was produced;fully soltion processing PLED including metal cathode was studied, and patterning anode forflexible OLED, at last, we researched their application form designing and preparing largewhite back light panel.Firstly, we studied the highly efficient, solution-processed WOLEDs based onfluorescent small molecules. The light-emission layer is realized by doping a fluorescentπ-conjugated blue dendrimer host (the zeroth generation dendrimer, G0) with ayellow-emitting fluorescent dopant oligo(paraphenylene vinylene) derivative CN-DPASDBwith a doping ratio of100:0.15(G0:CN-DPASDB) by weight. Our early study shows that G0device is hole dominated. Therefore, it‘s critical to suppress the holes while increase theelectrons to improve the device performance. To suppress excessive holes, thehigh-conductivity hole injection layer (PEDOT:PSS AI4083) is replaced by thelow-conductivity PEDOT:PSS CH8000. To facilitate the electron injection, a hybrid electroninjection layer is introduced by doping solution-processed cesium fluoride (CsF) into amethanol/water soluble conjugated polymerpoly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFNR2). The device achieves a maximum luminous efficiency of17.0cd A-1and a peak power efficiency of15.6lm W-1at (0.32,0.37) with a color rendering index of64. The deviceefficiency is highest ever reported for WOLEDs based on solution-processed fluorescentsmall molecules, which is also on par with the efficiency achieved by the thermallyevaporated fluorescent small-molecules.In order to get rid of the shackle of vacuum deposition equipmet, we introducedall-solution processed polymer light-emitting diode by solution-depositing the cathode andutilizing a multifunctional buffer layer between the cathode and the solution processedorganic layers. The buffer layer, which offers the functions of solvent-proof electron injectionand proper affinity, is fabricated by mixing the water/alcohol-soluble polymer PFNR2and acurable epoxy adhesive. The all-solution process eliminates the need for high vacuum forthermal evaporation of the cathode, which greatly reduced the production cost of organiclight-emitting diodes (OLEDs).To achieve roll-to-roll manufacturing, flexible substrates are needed. The application ofsolution process technology in flexilbe OLED making it possible to achieve wearable fantasydisplay in the future. There is a lot of problems in studying FOLED, the first problem ispatterning ITO anode. In the etching processing, the ITO film teared easily for the fragileproperty of ITO material. At last, bringing large leakage to the OELD devices. Especially,traditional etching processing, which possesses many steps and needs high temperatureannealing, make the ITO film crack much easier. To solve this problem, we invent a newetching method. Compared to traditional method, the new method which has fewer steps andlower temperature annealing is suitable for flexible OLED. In fivth section, we comparedflexible OLED devices‘J-V-L and LE-J characteristics curve between traditional and newetching method. Owing to the simple operation upon new etching mehod, the ITO film wassmooth and without burr and pinhole, the performance of flexible OLED devices are close tothe glass substrate devices. Based on the successful on subsize device, we designed and madeone inch red, green and white flexible OLED based on solution process.Moreover, for the application of WOLED, based on the Dr Junhong Zhou‘s work[1], wefurther improved the performance of lager area white back panel through adjusting thearrangement of metal grid in lighting area and treating organic layer with methnol or ethnolbefore evaporating metal cathode. We successfully prepared better performance four inchlager area white back panel.更多还原