This work was supported by National Science Council and Academia Sinica. We thank Prof. Yu-Tai Tao for his help with the fabrication and measurement of OLEDs.
Red-Emitting Fluorenes as Efficient Emitting Hosts for Non-Doped, Organic Red-Light-Emitting Diodes†
Article first published online: 14 FEB 2005
Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Advanced Functional Materials
Volume 15, Issue 2, pages 231–238, February, 2005
How to Cite
Chiang, C.-L., Wu, M.-F., Dai, D.-C., Wen, Y.-S., Wang, J.-K. and Chen, C.-T. (2005), Red-Emitting Fluorenes as Efficient Emitting Hosts for Non-Doped, Organic Red-Light-Emitting Diodes. Adv. Funct. Mater., 15: 231–238. doi: 10.1002/adfm.200400102
- Issue published online: 14 FEB 2005
- Article first published online: 14 FEB 2005
- Manuscript Accepted: 6 MAY 2004
- Manuscript Received: 10 MAR 2004
- Fluorescent materials;
- Light-emitting diodes, organic
Rare red-fluorescent fluorene derivatives have been designed and synthesized. The long-wavelength red fluorescence is achieved by incorporating a di(4-tolyl)amino or diphenylamino electron donor and a dicyanovinyl electron acceptor. The single-crystal X-ray structures of the di(4-tolyl)amino (pTSPDCV) and diphenylamino (PhSPDCV) compounds indicate only weak non-π van der Waals contacts in addition to long-distance dipole–dipole interactions of the red-emitting fluorene molecules in the solid state. The aggregation of the dipolar fluorene is largely suppressed by introducing bulky 9,9-substituents (spiro-fused bifluorene) as well as a non-planar di(4-tolyl)amino or diphenylamino group. In the solid state, these fluorene derivatives all show red fluorescence that is much brighter than with the red dopants Nile Red and DCM (4-(dicyanomethylene)-2-methyl-6-[4-(dimethylaminostyryl)-4H-pyran]). The unique photophysical properties of red-emitting fluorene derivatives differ from other known red dopants and facilitate the fabrication of non-doped red organic light-emitting diodes (OLEDs). Authentic red (CIE, x = 0.65, y = 0.35) electroluminescence with a brightness of more than 12 000 cd m–2 (greater than 600 cd m–2 at 20 mA cm–2) and a remarkable external quantum efficiency as high as 3.6 % have been observed for the red-emitting OLEDs with pTSPDCV or PhSPDCV as the sole emitting host.