Spiro-Host Materials for Blue Phosphorescent Organic Light Emitting Diodes
Ye-Xin Zhang, Xiang-Yang Liu, Zuo-Quan Jiang,* and Liang-Sheng Liao* Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China
*E-mail: zqjiang@suda.edu.cn, lsliao@suda.edu.cn
In recent years, phosphorescent organic light-emitting diodes (PHOLEDs) have drawn tremendous attention for the PHOLEDs can achieve theoretical 100% internal quantum efficiency which is much higher than fluorescent organic light-emitting diodes. Up to now, the PHOLEDs have made great progress in high efficiency and the progress is along with the developments of triplet host materials. Of these host materials, the spiro-hosts can easily acquire high glass-transition temperatures which are considered as important factors to the stabilities of materials. By incorporating 10-phenyl-9,10-dihydroacridine and fluorene moieties in spiro-linkage, we can get an effective building block, named SAF, for host materials. On the other hand, the substituted positions and/or the substituted groups should be carefully chosen to maintain high triplet energies which are required by blue triplet emitter. In this regard, a variety of host materials based on SAF core are designed and prepared. To extend the molecular size without reducing triplet energy, we can introduce other groups in different ways: either from the fluorene moiety or from the 10-phenyl-9,10-dihydroacridine moiety. As shown in the following figure and table, their molecular structures are depicted and some molecular physical properties are listed. Blue PHOLEDs were fabricated using these materials and iridium(III) bis(4,6-(difluorophenyl)pyridinato-N,C’)picolinate (FIrpic) as emitting dopant. Maximum efficiencies of 23.1%/51.5 cd A-1/46.7 lm W-1 were achieved using SAFPCz as host.
References [1] Y.-X. Zhang, L. Zhang, L.-S. Cui, C.-H. Gao, H. Chen, Q. Li, Z.-Q. Jiang, L.-S. Liao, Org. Lett. 2014, 16, 3748. [2] S.-C. Dong, Y. Liu, Q. Li, L.-S. Cui, H. Chen, Z.-Q. Jiang, L.-S. Liao, J. Mater. Chem. C 2013, 1, 6575. [3] Z. Jiang, Z. Liu, C. Yang, C. Zhong, J. Qin, G. Yu, Y. Liu, Adv. Funct. Mater. 2009, 19, 3987. [4] D. Lei, S.-C. Dong, Z.-Q. Jiang, H. Chen, L.-S. Liao, Adv. Funct. Mater. 2015, 25, 645.