高效量子点发光二极管的界面调控及全印刷工艺的研究

Low-cost printable displays and flexible displays are one of the top priority development areas in the next ten years, as stated in 《Made in China 2025》, a guideline to comprehensively upgrade Chinese industry. Colloidal quantum-dot light-emitting diode (QLED) is the ideal candidate for the development of next generation printable displays due to its advantages of high color saturation, tunable color, high efficiency, high stability and low fabrication cost via solution-processing...The aim of this project is to develop fully printable QLED with high efficiency and long lifetime. The efficiency of the devices is significantly affected by the interface defects, which quench the excitons. Also, there are no perfect solutions for the printable top electrode up to now, which limits the application of QLED in next generation printable displays...To solve these two problems, we propose studying the interface quenching mechanisms. By engineering the interfaces and reducing the defect density of ZnO, the quenching is expected to be reduced. We also propose using solvent-free Gallium-alloy with low melting point as the printable top electrode for QLED. With the printed Gallium-alloy top electrode, the fabrication of QLED does not need any vacuum systems, and thus it is completely compatible with the full-printing processes. By studying the surface properties of the Gallium-alloy printed electrode, and studying the interface properties of that between Gallium-alloy and carrier transporting layer, the efficiency and lifetime of the all-printed QLED would be significantly improved, which thus promote its application in next generation low-cost printable displays.

《中国制造2025》指出，在未来的十年，要大力发展低成本的印刷显示及柔性显示。量子点发光二极管（QLED），因具有发光色纯度高、效率高、稳定性好、可全溶液加工等优点，是印刷显示的最佳候选者。..项目的研究目标是实现高效率、长寿命的全印刷QLED。针对激子在界面处容易受到淬灭以及顶电极难于印刷制备的问题，提出：（1）研究激子在ZnO/QD界面处的淬灭机制，有针对性的修饰ZnO/QD界面，调控ZnO的缺陷态，以减少激子在界面处的淬灭，提高QLED的效能，并为高效器件结构的设计提供理论支持；（2）研究基于液态镓合金的可印刷电极及其在QLED中的应用，使整个QLED的制备完全省去真空蒸镀这一环节，实现真正的全印刷工艺，促进QLED在低成本、全印刷显示中的应用；（3）研究镓合金印刷电极的载流子注入能力，研究镓合金和载流子传输层的界面特性及其对载流子输运能力的影响，实现高效率、长寿命的全印刷QLED。

量子点发光二极管（QLED），具有发光色纯度高、效率高、可全溶液加工等优点，是柔性印刷显示的有力竞争者。本项目针对QLED器件性能低及器件顶电极难于兼容印刷工艺的问题，围绕高效QLED的界面调控及全印刷制备工艺开展研究，在QD/ZnO发光界面调控、正向老化（positive aging）机制、液态金属印刷电极及新型叠层QLED等方面取得突破进展。实现了外量子效率分别超过23.1%，27.6%，21.4% 及23.4%的红、绿、蓝、白四色QLED；实现了亮度超过160万尼特，同时外量子效率维持在10%的超亮高效QLED；实现了图形化精度达100 µm的液态金属电极及全印刷QLED。本研究所揭示的物理机制、所设计的器件新结构、所开发的制备新工艺、所建立的性能调控新策略广泛应用于高效长寿命器件的制备中；本研究为开发新型高效率长寿命QLED提供了理论指导与实验依据，也为柔性、印刷、透明等新型显示与照明的应用提供了新技术。