利用双线态激子发光的三苯基甲基自由基衍生物电致发光材料与器件研究

The commercial organic light-emitting materials and devices are based on the expensive and resource-scarce Ir or Pt complexes, and the basic patents are not occupied by our country. So developing cheap and high-efficient non-phosphorescent materials and devices is of great significance to the OLED industry in our country. How to utilize the triplet excitons with the ratio of 75 % in OLEDs is the key point of the study of high-efficient non-phosphorescent materials and devices due to that the transition of triplet exctions back to ground state is spin-forbidden.In this project,a new kind of OLED based on the emission of doublet excitons of conjugate free radicals is proposed. The problem of utilizing triplet excitons is circumvented. Because the reported light-emitting free radicals are concentrated in derivatives of (triphenyl)methyl radical,studing the effect of outer substituent group on the emission property of derivatives of (triphenyl)methyl radical and seeking the principle of designing highly efficient light-emitting free radicals are planned to carry out. High doublet exciton formation ratio (100 %) in conjugate free radicals based-OLEDs is expected through optimizing the structure of the devices.

已经商品化的有机发光器件（OLED），所用材料集中在昂贵并且资源稀缺的铱或铂配合物（磷光发光材料)上，并且我国不掌握核心专利，开发廉价并且具有自主知识产权的高效非磷光发光材料和器件对于助推我国OLED产业的发展具有重要意义。如何有效利用电激发条件下占比达75 %的三线态激子是高效非磷光发光材料和器件研究的关键问题（因为三线态激子向基态的跃迁是自旋禁阻的）。本项目提出基于共轭自由基分子的双线态激子发光（其向基态的跃迁自旋允许）的OLED发光新机理，避开了三线态激子利用的问题。由于目前能够发光的共轭自由基集中在三苯基甲基自由基衍生物上，本项目拟系统研究外围取代基团对三苯基甲基自由基发光性质的影响，总结高发光效率的共轭自由基的设计规律，获得具有高发光效率的三苯基甲基自由基衍生物；通过OLED器件的设计与优化，以三苯基甲基自由基衍生物为发光层，获得双线态激子生成比例接近100 %的OLED器件。

在本项目的资助下，开展了三苯基甲基自由基(TTM或PTM)衍生物发光材料与器件的研究，取得了如下的主要成果：1）通过总结高发光效率的自由基设计规律，获得了掺杂薄膜的光致发光效率达到90%的TTM-3NCz发光自由基材料，其发光器件的最大EQE达到27%，内量子效率接近100%的理论极限；2）提出利用给受体分子结构获得具有反构造原理电子结构的发光自由基，从源头上提高自由基分子的稳定性，并保持高发光效率，获得了系列具有反构造原理电子结构的高效高稳定发光自由基；3）提出利用发光自由作为敏化剂来提高传统荧光发光器件的效率，获得了最大EQE达到8.1%的荧光发光器件；4）区别于已广泛报道的三苯甲基发光自由基，开发了一个新的发光自由基体系，即二苯甲基发光自由基体系。