喷墨打印共混磷光有机小分子发光薄膜的聚集和相分离调控与器件性能研究

Aggregation and phase separation are the main reason for performance loss of inkjet printed small molecule based phosphorescent organic light-emitting diodes used host/dopant blending as light-emitting films. The mechanism of aggregation and phase separation of phosphorescent organic light-emitting blending films need to be researched and used to explore solution for controlling of the degree of films aggregation and phase separation. This is important to guide device performance improvement through combine with the research about relationship between films aggregation and phase separation and device performance. The main research contents of this project include: (1) The effect of some key elements, include molecular structure of host/dopant, solvents solubility and solution dispersing state and films forming dynamics, on aggregation and phase separation of inkjet printed phosphorescent organic light-emitting blending films and its action mechanism. (2) Developing of thermodynamics and dynamics methods which can be used to suppress aggregation and phase separation and improve microstructure uniformity for inkjet printed large area phosphorescent organic light-emitting blending films. (3) Relationship between films aggregation and phase separation and device performance can be formed through research about films photophysics and electronic performance. (4) Inkjet printing of phosphorescent organic light-emitting diodes with similar performance compared with their spin-coated counterparts through adjustment of films aggregation and phase separation.

喷墨打印共混磷光有机小分子发光薄膜中的聚集和相分离是制约器件电学性能提高的关键。理解喷墨打印共混磷光有机小分子发光薄膜聚集和相分离形成机理，掌握有效的调控方法，建立薄膜聚集和相分离与器件性能的关系，对打印器件的性能优化具有指导意义。本项目主要研究内容包括：（1）磷光主体/掺杂剂分子结构、溶剂溶解性和溶液状态、溶液到薄膜转变动力学过程对喷墨打印共混磷光有机小分子发光薄膜聚集和相分离行为的影响规律及其作用机理；（2）可抑制喷墨打印大面积有机小分子磷光薄膜聚集和相分离，提高薄膜聚集和相分离结构的区域分布一致性的热力学和动力学方法及其原理；（3）通过薄膜光物理和电学性质，建立薄膜聚集和相分离结构与器件电学性能的内在关联；（4）打印薄膜的聚集和相分离结构优化及与旋涂性能相当的有机小分子磷光器件的喷墨打印。

实现高发光效率的有机小分子磷光器件喷墨打印加工，必须解决有机小分子磷光薄膜的成膜性、膜厚均匀性和薄膜聚集/相分离等决定器件性能的关键问题。本项目针对喷墨打印共混磷光有机小分子发光薄膜中聚集/相分离及薄膜均匀性等导致器件性能严重降低的核心问题，研究可有效抑制喷墨打印共混磷光有机小分子发光薄膜聚集和相分离及提高薄膜均匀性的方法及其原理，实现均匀共混的无定形连续发光薄膜打印和高性能发光器件制备。我们首先通过调节溶剂与溶质分子的相互作用和分子在溶液中的分散状态等性质实现打印薄膜形貌调控，在此基础上，我们通过选择三相线固定型溶剂抑制打印超薄小分子薄膜去润湿，采用干燥过程中三相线固定的溶剂构建墨水，利用固定的三相线提高墨水干燥过程的液膜稳定性，实现了厚度接近10nm的超薄连续无针孔小分子发光薄膜打印制备。进一步通过构建弱毛细流动墨水提高打印薄膜均匀性，采用高粘度低挥发性良溶剂构建墨水的方法抑制咖啡环效应的产生，在兼顾抑制打印薄膜咖啡环效应改善薄膜厚度均匀性的同时，利用良溶剂促进溶液中的分子分散抑制薄膜中分子聚集，获得了厚度均匀的无定形发光薄膜，实现了打印器件性能的提高。