双极型芘衍生物的合成、分子结构及其光电性能研究

Organic light-emitting diodes (OLEDs) have attracted broad interests owing to their great potentials in future’s massive applications, e.g. next-generation full-color flat panel displays and solid-state lighting. Small molecules with bipolar transporting characteristics are considered as the key materials as they offer possibilities to achieve efficient and stable OLEDs even in a simple single-layer device. However, there are still technical and scientific challenges remaining, namely, low photoluminescence quantum yield (PLQYs), poor color purity and unclear charge-transporting mechanism of intramolecular charge transfer (ICT) state, etc. .The main focus of this project is to develop a novel regio-selective strategy for synthesizing small dipolar molecules as a high-performance electroluminescence material through asymmetrical functionalization of pyrene along Z-axis and by incorporating both electron-donating (D) and electron-withdrawing (A) group building blocks into 1,3-position and 6,8- (or 5,9-)positions..The major tasks will be to systematically investigate the effect of the substituted groups for the molecular conformation, electronic structures and photoelectric properties via a suitable choice of the D/A units; to fine-tune intramolecular charge transfer ability; to facilitate simultaneous manipulations of the HOMO-LUMO energy gap and the band width of light emission by ICT, to control crystallinity to be used to self-assemble molecular morphologies. The goal of this project is to obtain pyrene-based bipolar structure electroluminescence materials with high PLQYs for OLED application, which are of better solubility, air-stability and color purity. Additionally, to further solve the related scientificissues on molecular structure with functional regulatory of bipolar material, the relationship between the ICT state, charge-transporting properties and the molecular structures will be detail discussed.

双极主体材料能简化OLED器件结构并提高器件效率等成为有机光电子器件的关键功能材料之一。但该类材料及相关器件存在着荧光效率低、光色纯度差以及分子内电荷转移（ICT）态辐射跃迁机制不明确等科学问题。本项目旨在以制备ICT特征的高效固态有机发光材料为研究目标，创新性的沿芘环的Z-轴，利用立体控制，实现不对称功能化芘的1,3-和6,8-位（或5,9-位）。通过在特定位置有序的引入具有不同电子效应和空间效应的电子给体/受体基团，抑制固态下诸如聚集体或激基缔合物的形成，调节HOMO-LUMO能级，改善共轭体系中电荷传输的能力，提高材料的发光效率，实现对有机发光材料的颜色的精确调控，从而获得溶解性好、空气稳定、高色纯度和高固态量子产率的芘基双极发光材料。并围绕该类材料的结构和功能调控这一科学问题，把ICT特性,发光效率与电子传输性能结合,研究并解决ICT态双极材料所面临的相关科学问题。

芘是大π-共轭的稠环芳香烃化合物，拥有高荧光量子产率、高电子迁移率和空穴注入的能力。功能化芘环，制备高性能的双极型芘基有机发光材料，不但有效的抑制芘自身聚集导致的荧光淬灭，引入不对称单元，制备的双极型发光材料，还能有效的调节分子能级、改善电荷的传输能力，提高材料的效率。.围绕上述研究目的，本项目开展了：（1）利用立体控制方式，调控不同电子性质的推拉取代基团，调节给体/受体的种类、大小等，调节HOMO和LUMO能级，成功制备了不对称的芘基衍生物，此类衍生物表现出优异的双光子性能，最大的双光子界面高达1348GM，扩大了芘化学的应用范围；而且能够通过构建不同分子构型的发光材料，实现目标材料颜色宽波段可调，稳定性好的分子内电荷转移发光材料；（2）基于芘的特殊电子效应，在2,7-位分别引入不同发光颜色的四苯基乙烯（TPE）衍生物，构建了新型不对称取代的芘基发光材料，该类化合物表现出明显的聚集诱导发光性质，且实现了芘基发光材料的白光发射；进一步，在芘的2,7-位分别引入具有蓝光性质的四苯基乙烯基，制备了高性能的芘基聚集诱导蓝光分子，其电致发光的最大发射在492nm，最大发光强度位15750 cd m-2，为进一步构建高效芘基聚集诱导蓝光材料提供了分子设计思路。（3）设计合成新型芘基六芳基苯（HAB）衍生物，并且在此化合物中观察到了多重光致发光现象，其中包括单体发射，准分子发射和电荷转移发射过程；（4）、基于吡啶基中氮原子的取代位置不同，产生不同的电子效应，影响自身的酸度系数（pKa），构建具有聚集诱导发光性能的荧光探针，不但拥有明显的AIE特性，能够专一的、高灵敏度、快速的检测溶液中的Fe3+。而当TPE-o-Py遇到癌症细胞中的Fe3+时，荧光颜色能够从蓝光转变为橙红光，实现癌症细胞中铁离子的检测。本项目所取得的研究成果，将推进芘化学为主体的有机发光材料的发展，并实现其商业化应用提供知识储备和技术手段。