基于分子自封装构筑高效稳定的宽带隙聚芴半导体

The stability and efficiency of wide-bandgap light-emitting polymers has been a long-standing challenge for industrial and fundamental researchers in plastic electronics, which severely limits their commercialization in solid-state lighting and information displays. In fact, as the most potential application of wide-bandgap light-emitting polymers, the aggregation-induced quenched emission and chemical/morphological stability of deep-blue polyfluorenes are the key factors to not only induce their instability and low luminescent efficiency but also result into the lower yield or reproducibily of large-scale high-quality active films and light-emitting devices. In this project, we originally proposed a supramolecular self-encapsulation strategy for controlling interchain interactions in the solid state to construct wide bandgap polyfluorenes via the bilateral asymmetrical molecular design. Firstly, we will design novel high performance and stable polyfluorenes with the incorporation of diphenyl groups as steric repulsors at 9-position and charge transport aromatic groups as the attractor at the 4-position via bilateral asymmetrical funactionalization of fluorene monomers. An excellent self-assembly behavior of self-encapsulated polyfluorene allow for a strong secondary interaction (π-π stacking) of pedant charge-transported groups, which can induce chain self-assembly into a protective sheath, not only to inhibit interchain interaction and enable intrachain emission behaviour but also to improve spectral and morphological stability and interchain charge transport (via constructing two-dimensional charge transport channels). Large-scale, uniform and stable emitting films will be also constructed with film-thickness independent emission. Finally, large-scale flexible stable and efficient deep-blue polyfluorene-based polymer light-emitting diodes (PLEDs) with electroluminescence (EL) featuring the intrachain excited state will be fabricated via optimizing solution formulation and film-processing technology.

宽带隙蓝光聚合物的性能与稳定性问题，是目前限制发光聚合物半导体应用于信息显示和固体照明的主要瓶颈，也是目前学术界和工业界面临亟待解决的重要课题。作为最具应用潜力的宽带隙聚合物，聚芴主链间聚集作用和结构易被氧化是诱导其低效率和不稳定发光的根源，也是降低高质量薄膜和器件大面积制造良率的重要原因。基于此，申请人提出通过主链双侧不对称分子设计理念，通过分子自封装策略构建高效稳定聚芴半导体。首先，借助芴单元不对称功能化，在分子主链的9位和4位引入位阻基团和载流子传输基团，制备一系列高效稳定聚芴半导体；借助芴4位稠环基团组装形成封装层，搭建载流子二维传输通道的同时抑制主链间的聚集作用，实现分子主链自包覆和单分子机制的激光态光物理行为，提高薄膜的化学和发光稳定性、以及发光效率；通过优化溶液配方和加工工艺，精确控制薄膜下分子链封装过程，实现发光厚度不敏感薄膜的大面积制造，应用于柔性大面积发光光电子器件。

作为一类重要的蓝光聚合物，聚芴材料由于高荧光量子效率和深蓝光发光，在聚合物发光二极管和激光领域具有重要的应用前景。在本项目的支持下，申请人已发表30余篇论文，包括Chem、Light: Science & Applications、Advanced Materials、Research、CCS Chemistry、Macromolecules、National Science Review、Science Bulletin、Advanced Functional Materials、Advanced Science、Nano Energy、Chemistry of Materials、Advanced Optical Materials等。在本项目的资助下，申请人紧紧围绕围绕着蓝光聚合物及其PLED的高稳定化、高性能化、柔性化方面取得的主要代表性成果有：（1）、阐明缺陷态结构形成导致蓝光聚合物及其PLED稳定性和效率受限的问题机制，构建基于平面化构象的多级有序结构发光中心，实现器件稳定批次发光、窄光谱(<15 nm)高效蓝光，有效提高蓝光PLED工作稳定性和转换效率（>3倍）；（2）、针对发光层中痕留缺陷和器件批次重复性差问题，提出链自封装策略实现单链激子限域发光新机制，从源头抑制缺陷态形成，使发光层表现出优异蓝光的老化稳定性、良好的电致蓝光制备重复性，提高蓝光PLED的性能和制造良率；（3）、面向柔性发光技术，针对柔性器件工作中层间存在应力不平衡问题，直观论证并发展超分子功能化策略构建本征柔性蓝光发光分子，兼具高稳定、高效率（~90%）和本征柔性，提高柔性发光体应力耐受性，构建柔性发光器件，对于进一步构筑高效稳定柔性发光器件具有重要意义。在本项目资助下，申请人构筑一系高性能芴基蓝光材料与发光器件，将有助于推动塑料光电子的产业化。