超低电压蓝光量子点发光二极管的器件结构及电致发光机制研究

The quantum dot light emitting diode (QLED) is an electroluminescent device using quantum dots as a luminescent material. QLED promise numerous advantages such high stability, color tunability, wide color gamut, low energy consumption, flexibility shape and so on. QLED also brings together the advantages of both light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), making it a new research direction for future display and lighting. But for now, a serious technical problem for QLEDs is blue QLEDs with high driving voltage, low brightness, low efficiency and short life. This seriously hinders the rapid development and commercial applications of QLEDs. Therefore, this project intends to systematically study on the synthetic method of blue quantum dots and improvement of their fluorescence quantum yield. We will also investigate the method of fabrication of blue QLEDs and their electroluminescence mechanisms. In addition, we plan to exploit interfacial Auger-electron injections to reduce the driving voltages significantly, and fabricate blue QLEDs with device working voltages below the energy gap of quantum dots. This proposed research will help promote the application and popularization of QLEDs for thin film display, touch screen display, healthy lighting, biomedical and other fields of application.

量子点发光二极管（QLED）是一种以量子点作为发光材料的电致发光器件。QLED集成了发光二极管（LED）和有机发光二极管（OLED）两者的优势，具有高稳定性、颜色可调、色域广、能耗低、可作柔性器件等优点，是未来显示和照明的发展方向。但目前QLED的技术难题是蓝光QLED存在驱动电压高、亮度低、效率低、寿命短的问题，这严重阻碍了QLED的发展及商业化应用。本项目拟从无镉蓝光量子点和蓝光QLED器件制备入手，研究提升量子点荧光量子产率的有效方法以及蓝光QLED的器件结构和电致发光机制，并利用器件中不同薄膜界面的俄歇电子注入使驱动电压大幅度降低，进而研制出驱动电压低于量子点能隙值的超低电压蓝光QLED器件。这对实现高效、节能的QLED显示器和发光器件是一项重大突破，它可推进QLED在薄膜显示、触摸屏显示、健康照明、生物医学等众多领域的应用和普及。

以含糖、氨基酸的有机小分子等材料作为碳源，经过加热、脱水、缩合、碳化等过程，成功制备了尺寸可控的碳量子点，系统地研究了反应条件对量子点大小的影响以及官能团修饰和掺杂对碳量子点的发光性能的调控作用，制备了具有高色纯度的蓝色荧光碳量子点。利用柠檬酸和二氨基萘作为碳源的最佳方法，利用热处理合成了含-OH、-COOH及-NH2等官能团的碳量子点，研制了具有高量子产率的的深蓝色碳量子点，该量子点具有半峰宽为35 nm的荧光发射峰、高达70%±10%的光致发光量子产率、色坐标接近（0.15, 0.05）等优良特征。并设计制备了高性能QLED器件。通过结构优化，深蓝色OLED器件的最大量子效率达4%，对应电流效率为2.6 cd A-1，最大亮度为3715 cd·m-2，并利用多种表征方法研究了多层膜的结构特征及器件的发光性能。理论上系统地研究了器件中有机/无机、有机/有机界面的能级排布规则，对供体-受体分子电子过程、电荷转移规律进行了系统研究。通过对QLED器件的发光性能测试，利用XPS/UPS能谱、设计单功能器件，进一步验证了器件中异质结界面的能级排布准则的普适规律，为制造有机半导体材料的选择和光电器件的设计提供了指导。