基于高量子产率(>90%)核壳结构量子点的高效全彩发光二极管

Quantum dot-based light emitting diodes (QD-LED), with their good monochromaticity, high color purity, low power consumption, and long lifetime, are considered as a promising light source for the next generation solid-state lightings and displays. However, the low light emission efficiency of red, green, and blue QD-LED and the low brightness in violet-blue region limit the application of QD-LED. To address these issues, the design and synthesis of high quantum yields (QYs) QDs, the precise adjustment of the workfunction of charge transport materials and the matching of energy levels of the electron/hole injection layers with the emissive QD layer would be the most important elements. In this project, core/shell structured quantum dots with QYs beyond 90% is selected as the emitting materials. By using such self-designed and self-synthesized high quality QDs, shell materials can be designed specially towards the precise bandgap tuning of the core-shell QDs to realize the exact matching of the energy level between the transport layers and emissive QDs. Furthermore, suitable but highly conductive organic/inorganic ligands would be adopted to replace the traditional insulating long chain ligands on QD surface and thus shorten the energy transport path without compromising the emission stability and QYs of QDs. All these works are aimed to the effective improvement in efficiency of full-color QD-LEDs. Theoretical simulation will also be used to obtain the optimized model with best matching of energy levels between the transport and emissive layers in QD-LED.

基于荧光量子点的二极管（QD-LED）新型显示器件，具有单色性好，色纯度高，耗电量少、寿命长等优点，有望成为下一代固态发光和平板显示的主流技术。当前三基色QD-LED的发光效率及蓝紫色发光区域亮度相对偏低，是阻碍相关器件进入实际应用领域的主要障碍。如何通过调控QD-LED器件结构中传输介质功函及电子和空穴注入层与量子点发光层之间的势垒匹配获得高效高亮QD-LED器件是关键的科学问题。本研究拟采用量子产率大于90%的核壳结构量子点通过精确的实验设计来调控量子点的能级，并采用有针对性设计的壳层材料来实现器件中各功能层之间的能级匹配，并通过对量子点表面的长碳链修饰配体的取代来获得拥有高电子输运功能的短链有机或无机配体修饰的量子点，在保证发光稳定性和效率的同时有效缩短发光层中量子点之间的能量传输路径，进而获得高效率的全彩QD-LED器件，结合理论模拟获得QD-LED各功能层之间的最佳能级匹配模型。

基于本项目的实施，在提高蓝绿红QD-LED的发光效率、亮度和稳定性等方面，取得了系列较好的进展。提出调控发光层适配传输层的器件构筑思路，解决了以往QD-LED器件中高效率时亮度低（<2000cd/m2），只适用于低亮度显示而不适用于高亮度显示和照明应用的难题。在国际上率先报道了适用于QD-LED的量子产率大于90%的高稳定非闪烁核壳结构系列量子点材料的可控制备。发展了系列QD-LED构筑技术，蓝色QLED的外量子效率国际上率先突破10%，国际上率先实现红色和绿色QD-LED外量子效率同时达到20%，是目前红色和绿色QD-LED效率，亮度，以及红绿蓝QLED寿命最高纪录的保持者。项目执行期间，第一/通讯作者发表包括Nature Photo., Nano Lett.，Chem. Mater.，Laser Photonics Rev., ACS Photo.等在内的SCI论文19 篇，其中SCI一区论文15篇，二区论文4篇，申请专利10 项，授权4 项。2篇论文入选ESI “Highly Cited Papers” 。