中性单核锰(II)配合物发光材料的合成、表征及器件制备

In this project, we choose cheap neutral Mn(II)-based small molecules as a light-emitting layer to replace the expensive Ir(III) and Pt(II) complexes used in organic light-emitting diodes (OLEDs) to reduce the price of the commercial products. In order to obtain neutral Mn(II)-based luminescent materials, a series of rigid chelating ligands containing two P=O groups are designed and synthesized, and halide ions as counterpoise anions are introduced to coordinated with center Mn(II) cation. The structures and photophysical properties of the obtained materials are performed by means of single crystal x-ray diffractometer, UV-visible absorption and fluorescence spectrometer. The ground- and excited-state electronic properties are calculated by DFT method. We investigate the impact of the position and types of substituent groups, bridging atoms, distances between two P=O groups and the types of halogen ions on luminous properties, such as maximum peak position, photoluminescence quantum yield (PLQY) and lifetime. The materials with high PLQY(more than 80%) and good stability are selected as emitters to prepare OLEDs with the highest external quantum efficiency over 10% by means of spin-coating and vacuum thermal evaporation processes. The effects of technologic parameters on the device efficiency and lifetime are investigated, such as solution concentration, spin speed and time, thermal evaporation rate and film structure. Therefore, the implementation of this project not only has a great theoretical significance for a deeper understanding the luminescence mechanism of neutral Mn(II) molecules, but also gives a good opportunity for the development of commercially available low-cost Mn(II)-based emitters used in OLEDs in the future.

本项目以廉价的中性单核锰(II)配合物分子作为发光层，替换商业化产品中昂贵的贵金属铱(III)和铂(II)配合物发光材料，降低商品价格。设计包含两个P=O基团的刚性螯合配体，引入可平衡电价的卤素离子参与配位，得到中性单核锰(II)发光材料。利用单晶衍射仪、紫外—可见吸收和荧光光谱仪等手段获得材料的结构和光物理性能。结合DFT计算，研究配体取代基位置和种类、桥联基团、P=O基团间距以及卤素离子类型等因素对发射峰位置、量子产率和发光寿命的影响。选取光致发光量子产率高于80%且稳定性好的材料，利用溶液旋涂和真空热蒸镀工艺，制备最高外量子效率大于10%的器件。考察溶液浓度、旋涂速度和时间、热蒸发速率、膜厚和传输材料等参数对器件效率和寿命的影响。本项目的实施对深入理解中性单核锰(II)分子的发光机理具有重要理论意义，且为今后开发可产业化的廉价锰(II)基发光材料打下坚实基础。

本项目设计包含P=O基团的有机配体，在溶剂热条件下，与卤化锰反应，得到系列强发光的锰(II)配合物发光材料。考察了P=O基团间距和位阻、溶剂种类、取代基大小、重原子效应等因素对所得产物结构和发光效率的影响。选取高发光量子产率的材料，利用热蒸镀法和溶液法，制备了电致发光器件。. 本项目的主要研究内容和重要结果如下：.(1)P=O基团间距和位阻。邻位易于形成零维的小分子，而间位更倾向于形成一维的链状聚合物。同时，用位阻小的甲氧基置换苯基，得到多核的中性分子，但是发光效率大大降低。.(2)溶剂种类。溶剂分子的不同，会导致材料从不发光逐渐变为强发光，且发光颜色在绿光和红光范围内变化。.(3)重原子效应。除了经典的卤素重原子效应，本项目的一大发现是配体内部有重原子时，比如氮原子置换碳原子，化合物发光量子效率的提升更加明显。但是，当氮原子与锰配位时，会猝灭发光，导致得到的材料在室温下不会发光。.(4)在研究内容(3)的基础上，发现含吡嗪基团时，配体本身具有光致变色现象，为开拓光致变色体系提供了新的思路。.(5)以高量子产率的配合物作为发光层材料，考察了不同的主体材料、空穴传输材料和电子传输材料等工艺对电致发光器件性能的影响。. 本项目的研究结果为设计高量子产率的锰基发光材料及其在电致发光器件中的应用打下良好的基础。发现P=O基团取代的吡嗪分子具有光致变色现象，为拓展光致变色体系开辟了新的路线。