湿法加工的阴极在大面积全溶液加工有机白光器件中的应用研究

As a new technology in the solid state lighting, organic light emitting diode (OLED) attracts enormous attentions from both the academy and the industry, due to its simple fabrication process, low cost, flexibility, etc. Compared to the vacuum evaporation process, the solution process, such as spin-coating, inkjet printing, blade coating, slot-die coating, dip-coating, etc., offers the advantages of low equipment investment, high yield, low material consumption, and easiness to realize large area. However, even in the solution-processed OLED devices, the metal cathode is still deposited through vacuum evaporation process. To deposit the metal via solution process, it requires that the conducting ink has to form a continuous solid film on the organic layer, and possess good electric conductivity，high reflectivity, and low absorption. In addition, since all the stable solution-processed metal inks are made of high work function metal, such as silver, gold, copper, etc., the electron injection from the high work function metal cathode into the organic function layers is difficult. Therefore, interface engineering is required to modify the organic/metal interface to enhance the device performance, for example, integrating electron injection layer. Moreover, OLED is thin film device in which the functional organic layer is only a few tens nanometers thick and the organic doesn’t have mechanical strength, can’t tolerate high temperature, and is very sensitive to the solvents, the solution process of the top electrode has to be friendly to the organic layers underneath. In our application, we propose the application of solution-processed metal cathode in the large area solution-processed organic solid state lighting panel. We still study the dependence of the film quality on the metal inks’ fluid properties and the solvent evaporation rate, investigate the physical mechanism of the electron injection layer, explore the aging process of the all solution processed WOLED device, determine the best solution process to deposit the metal cathode, and develop a mature process to fabricate high efficiency, stable, and large area WOLED lighting panel.

有机电致白光器件（WOLED）作为新一代固态照明光源技术，有着超薄、高效等优点。虽然溶液加工型WOLED以设备投资小、易实现大面积等优点弥补了真空蒸镀工艺的不足，但其阴极仍需要真空蒸镀工艺。要实现金属阴极的湿法加工：不但要求良好的湿法加工特性和铺展成膜性，还要求成膜后具有高导电率和反射率。另外可湿法加工的电极材料通常由金银铜等高功函金属构成，不利于电子注入，还需要通过界面工程的方法来提高器件性能。此外，由于有机功能层只有几十纳米，机械强度低，不耐高温，对溶剂敏感，所以在有机层上方进行湿法加工金属阴极非常具有挑战性。本项目拟研究大面积湿法加工的金属阴极在WOLED中的应用，通过总结不同导电墨水的流体和溶剂挥发特性与成膜质量之间的规律，深入研究阴极界面修饰层的电子注入机理并建立相应的物理模型，探索分析全溶液加工WOLED器件的老化机制，掌握全溶液加工大面积WOLED的工艺，实现高效稳定器件

国家自然科学基金资助项目“湿法加工的阴极在大面积全溶液加工有机白光器件中的应用研究”（51573056）已于2019年底顺利完成。在过去的四年中一共发表15篇SCI检索论文，其中包括8篇一区，4篇2区。6名博士研究生和1名硕士研究生在基金资助下顺利毕业。.有机电致白光器件（WOLEDs）作为新一代固态照明光源技术，有着超薄、高效等优点，但其阴极制备仍依赖于真空蒸镀工艺。深入研究器件阴极界面特性并建立相应的物理模型，掌握全溶液加工大面积WOLEDs的工艺，是实现低成本、大面积制造WOLEDs的关键。.在阴极界面物理领域，我们创造性地利用掩膜阴影和金属蒸气的散射效应，在有机衬底表面真空沉积超薄的、厚度渐进变化的金属Al层，以研究有机材料与后蒸镀 Al 电极之间形成的偶极层的取向与大小。实验发现，有机材料的极性成分决定了其在金属界面上的偶极取向，不同的金属生长形貌和镜面电荷效应强弱等因素则会影响形成的偶极大小。该实验进一步完善OLEDs阴极界面物理模型。.在全溶液加工器件领域，我们开发了一种新型的有机/无机杂化的PFN-OX/ZnO结构电子注入层。这种电子注入层兼具有机电子注入层高效的电子注入能力以及无机电子注入层优异的抗溶剂侵蚀和阻挡溶剂的能力，能够帮助全溶液加工器件获得更优的器件效率以及更低的工作电压。基于此，全溶液蓝光OLEDs实现电流效率2.1cd/A、亮度4.9×103 cd/m2，启亮电压为4.0V。.与此同时，我们将OLED全溶液加工方案应用于量子点发光二极管（QLEDs）以及钙钛矿发光二极管（PeLEDs）中，成功制备了外量子效率为12.7%的全溶液倒装红光QLEDs，以及外量子效率为4.66%的全溶液绿光PeLEDs，均为当时报道的最高值。.最后，为了推进成果向实际运用转化，我们还将全溶液加工方案运用于大面积白光照明板中，成功制得了4英寸的白光板。