基于高质量CuInSe2核壳结构量子点的深红-近红外发光二极管

Deep-red and near-infrared quantum dot light-emitting diodes (QLEDs) have been widely applied in optical communications and computing, biomedical imaging, night vision and the next generation flat panel display. Currently, the performance of deep-red and near-infrared LEDs based on Cd- and Pb- QDs is poorer than that of visible QLEDs, which is attributed to the lower quantum efficiency of QD films and imbalanced charge injection. Furthermore, these devices have been limited to applications in the real life, due to the heavy metal elements of Cd and Pb. In this project, high-quality and low-toxity CuInSe2 QDs, along with high quantum efficiency, narrow bandwidth and emission tunability, will be synthesized through precisely controlling the shell materials, components and shell thickness, and then, to improve the charge-injection balance by tuning the matching of energy level between transport and QD layers. Meanwhile, tetrabutyl ammonium halide, ethanedithiol and ethylenediamine will be used to modify the QD surface by the solid-state ligand exchange to improve the carrier transport efficiency, and further to improve the matching of energy level between transport and emissive layers, aming to enhance the brightness and radiance. This work would be expected to provide the material and theoretical support and possible technical approaches for the high-performance CuInSe2-based deep-red and near-infrared QLEDs.

深红-近红外量子点发光二极管（QLED）在光纤通讯和计算、生物成像、夜间探测以及下一代平板显示等领域具有广阔的应用前景。目前，基于Cd、Pb类量子点的深红-近红外QLED由于薄膜的荧光量子产率低、器件中电荷注入不平衡等因素使得器件性能远低于可见光QLED，且由于Cd和Pb等毒性重金属元素的存在会进一步阻碍此类器件的实际应用。本项目拟通过精确调控量子点的壳层材料种类、组分和厚度合成高质量、低毒的CuInSe2核壳结构量子点，使其具有高荧光量子产率、窄半峰宽，且发光峰连续可调；调控量子点层和电荷传输层之间的能级匹配度，提高载流子的注入平衡，提高QLED器件效率；采用四丁基卤化铵、乙二硫醇和乙二胺等对量子点表面进行固态配体交换，在提高载流子传输效率的同时进一步改善传输层和量子点层的能级匹配性，提高器件亮度。为发展高性能CuInSe2基深红-近红外QLED提供材料和理论支撑，探索可能的技术途径。

基于量子点的发光二极管（QLED）由于具有色纯度高、稳定性好等一系列独特优势，现已成为下一代平板显示和固态照明领域最具潜力的发光显示技术。本项目以CdSe体系量子点为基础，在无TOP/TBP法合成高质量量子点的基础上，基于壳层调控策略，获得了一系列量子产率90%以上、稳定性好，且荧光峰位覆盖可见-近红外光区的CdSe基核壳结构量子点（CdSeS、ZnCdSe、CdTe/CdSe等），首次合成了无壳层包覆、具有单通道荧光衰减的非闪烁量子点，获得了适配空穴传输层能级的壳层材料和组分，明确了壳层材料、组分和厚度与器件性能的关系。针对量子点层电荷传输速率低的问题，我们采用短链有机配体和/或无机配体对量子点表面进行修饰，提高了空穴注入效率和电荷迁移率，促进了载流子注入和复合平衡。从而获得了具有抑制效率滚降的高性能可见-近红外QLED，其中红色QLED的外量子效率（EQE）超过30%；绿色QLED在亮度67,800 cd/m2时获得最大EQE 22.9%；蓝色QLED的亮度达到52,360 cd/m2，并且在100~10,000 cd/m2的较大亮度范围内EQE均达到显示和照明的应用要求；同时，CdTe/CdSe近红外QLED的器件效率达到7.2%。基于上述壳层调控策略，我们获得了尺寸~8 nm、量子产率~80%、荧光覆盖640~800 nm的Zn:CuInSe2/ZnS//ZnS核壳结构量子点，解决了以往CuInSe2系列深红-近红外量子点的量子产率普遍较低（近红外发光区小于60%），粒径小（通常小于6 nm）且不均匀的问题。相应地，基于Zn:CuInSe2/ZnS//ZnS核壳结构量子点的近红外QLED，其效率达到4%，是无Cd体系近红外QLED器件的最高效率。上述研究工作为实现高性能、长寿命的QLED器件提供了一定的材料基础和理论支撑。