全石墨烯电极柔性透明有机发光器件研究

Organic light-emitting diodes (OLEDs) have attracted considerable attention as the next-generation display technology due to the self-emitting, light weight, high flexibility, low thickness, low electric power consumption, good contrasting colors and wide color gamut. Transparent OLED (TOLED) is a breakthrough transparent display technology that displays dynamic or interactive information on a transparent substrates. This revolutionary display allows users to view what is shown on a video screen while still being able to see through it. Flexible TOLEDs (FTOLEDs) perform amazing potentials as candidates for AR/VR technology, smart glasses, window display, smart windows, head-up displays on car windshields and so on. Unlike the traditional OLEDs fabricated on rigid glass with an indium-tin-oxide (ITO) transparent conductive electrode (TCEs), the fabrication of flexible OLEDs requires TCEs with superior mechanical flexibility, electrical conductivity and optical transparency to replace ITO. Graphene, a monolayer of carbon atoms arranged in a honeycomb structure, is an ideal material to fabricate flexible TCE due to its outstanding properties, such as a transmittance of 97.7%, a carrier mobility of 10^6 sq. cm/Vs, an intrinsic tensile strength of 130 GPa and a Young's modulus of 1 TPa. In this project, graphene is used as the TCE material to fabricate flexible and transparent OLEDs. Here, we will optimize electrochemical bubbling delamination graphene transfer technology to obtain clean and high quality bottom graphene electrode, develop new graphene transfer technologies to fabricate top graphene electrodes on organic layers, investigate doping methods to adjust the sheet resistance and work function of graphene. Next, we will fabricate flexible and transparent OLEDs based on graphene anode and cathode electrodes. Furthermore, we will improve device efficiencies and mechanical properties via optimizing device configuration, such as utilization of hole- and electron-carrier injection layers. The to-be-developed graphene transfer technology and all-graphene electrode OLEDs fabrication technologies can simplify device fabrication process, reduce the production cost, improve productivity, and prolong device lifetime. The flexible and transparent properties enable the creativity of new display designs of OLED technology.

柔性和透明有机发光二极管（FTOLED）不仅具备OLED产品固有的轻薄、能耗低、对比度高等特点，更以未发光像素呈现高透明状态的特性在未来显示领域展示出强大的吸引力。本项目选用石墨烯作为阳极和阴极材料制备FTOLED器件。首先，探索可以替代聚甲基丙烯酸甲酯（PMMA）转移石墨烯的聚合物，解决石墨烯表面PMMA残余问题，制备高质量、洁净底端石墨烯电极；其次，发展边框辅助法，解决石墨烯转移过程对有机光电材料的损害问题，制备顶端石墨烯电极；再次，通过石墨烯的表面修饰调节其面电阻和功函数，实现石墨烯电极和有机层的欧姆接触；然后，使用本项目发展的石墨烯转移和表面修饰技术制备全石墨烯电极FTOLED器件；最后，结合器件结构优化方案开发出发光、机械性能良好的全石墨烯电极FTOLED器件。本项目开发的石墨烯转移和器件制备技术可以简化器件制备工序，降低成本，提高生产效率，为进一步推动其产业化发展做出一定贡献。

有机发光二极管（OLEDs）以其轻薄、能耗低、对比度高等优异性能在显示领域展示出强大的竞争力。柔性OLED器件不仅具备OLED产品固有性能特点，而且以可弯曲等特性使其在可穿戴设备和VR/AR设备、智能眼镜、智能窗口等未来显示领域的应用成为现实。由于ITO电极弯折易碎、原材料稀少，不适于应用于柔性光电器件，过去的十年中，寻求替代ITO的透明电极材料成为研究的热点。到目前为止开发的主要透明电极材料有半透明金属薄膜电极，金属纳米线，金属网格，导电氧化物，导电聚合物，碳纳米管和石墨烯等。其中，石墨烯是一种碳原子呈蜂窝状排布的单原子层二维结构，具有很好的化学可修饰性、高载流子迁移率、卓越的机械柔韧性以及高透光率等独特的物理特性。本项目聚焦透光率高、导电和机械性能良好的石墨烯作柔性透明电极，围绕石墨烯转移、改性以及有机发光器件应用和高性能化等关键问题开展了较为系统的研究工作，在理论与技术创新方面取得了重要进展。发现了负微分电阻现像，揭示了其起源并提出电流预扫描去除法，降低了器件性能对石墨烯质量的高度依赖。发展了电化学鼓泡和“二合一”石墨烯转移技术，克服了传统石墨烯转移技术成本高、效率低、质量差等问题，大幅度提升了石墨烯的转移效率和质量。提出了磷钼酸表面电荷转移掺杂和高介电常数聚合物构建界面偶极的石墨烯表面修饰方法，实现了石墨烯面电阻的显著降低和功函数的有效调控。并成功的将发展的石墨烯转移技术和表面修饰方法应用于有机发光器件，结合“梯度空穴注入层”结构，掌握了高性能柔性石墨烯有机光电器件制备技术，其中白光有机发光器件效率高达326.5 cd/A和128.2 lm/W，综合性能达到同期国际领先水平。