基于胶体量子点的高效率白光混合LED的研究

Results from the previous project have demonstrated that phosphorescent sensitization can effectively improve performances of hybrid light-emitting devices (LEDs) based on the emission of quantum dots (QDs). Meanwhile, energy transfer (ET) from organic phosphorescent dyes (PDs) to QDs strongly depends on the molecular structure of PDs. Therefore, we plan to study the ET between PDs and QDs more deeply to further understand its mechanisms and quantitatively measure its F?ster radii. We also plan to investigate the ligand exchange of QDs to synthesize QD-PD materials and QD-polymer materials. The former could be used to quantitatively measure F?ster radii of ET between QDs and PDs and to fabricated hybrid LEDs as emitting materials. The latter could be used as a single emitting material without phase separation during the fabrication to fabricate hybrid LEDs with high performances. Since solution process is necessary to deposit QD-films due to the large molecular weight of QDs, it is essential to combine the solution processed QD-emission-film with the vacuum deposited charge-transporting layers for the fabrication of hybrid LEDs with multilayer structure. In this project, we plan to achieve this goal by using micro-contact printing technology. The key process of this technology is the formation of smooth close-packing QD-film, which we plan to perform by using layer-by-layer deposition. Besides the formation of QD-films, layer-by-layer deposition is also planned to construct alternate single-molecule-layer of QDs and PDs for the measurement of F?ster radii between them.

青年基金的前期研究证实了磷光敏化可有效地提高基于量子点发光的混合LED的性能，同时，有机磷光材料到量子点的能量转移强烈依赖于前者的分子构型。因此，本项目拟对磷光材料到量子点的能量转移进行更深入的研究并实现定量测量；拟通过对量子点配体交换的研究合成量子点-磷光材料或量子点-聚合物材料。前者可用来定量研究磷光材料到量子点的能量转移和直接用作混合LED的发光材料；后者可以用来解决发光层中的主体和量子点的相分离问题，从而提高器件的色纯度和效率。量子点的大分子量决定了这种材料只能采用溶液法成膜，为了将真空沉积形成的载流子传输层与溶液法形成的发光层相结合，我们拟采用微接触印刷技术。其关键是均匀致密的量子点薄膜的形成, 在本项目中我们拟采用逐层沉积技术实现。除了用作形成量子点薄膜，逐层沉积技术还可用作构筑交替的量子点和磷光材料的单分子层以定量测量二者之间的能量转移。

本研究是申请人青年基金项目（60906021）的延续。以采用金属配合物量子点材料作为发光材料的白光器件为主要研究方向，开展了一系列相关的研究，获得了预期的研究结果，发表了一批有影响力的论文，对项目的成果转化做出了重要的贡献。首先，我们采用香港大学支志明院士课题组开发出的一系列高效率的具有刚性四齿配体的铂配合物作为发光材料，通过器件物理的研究实现了高效率的单体和聚集态平衡发光的白色发光器件，这是目前为止文献可见的最高效率的单发光材料的白光聚合物发光器件。该系列材料和器件在有机发光，特别是白色有机发光领域，具有极大的应用潜力并因此获得了国内外相关企业的关注，实现了成果转化。同时，我们利用金配合物的长激发态寿命和高效率发光提出了一个崭新的调光机理，实现了国际最高效率的光色可调的有机发光器件。最后，我们利用高效率的廉价的分别以锌和铜为中心原子的两个系列的金属配合物首次实现了低成本的全廉价金属配合物的采用溶液法制备的白光器件。其中锌配合物具有高效率的蓝色荧光发光，而铜配合物是高效率的黄光材料。