We thank the National Science Council for financial support. Our special thanks go to Professor C.-H. Cheng, Dr. J.-P. Duan, and Dr. H.-T. Shih for their support and cooperation during the preparation and characterization of the light-emitting devices.
Color Tuning of a Light-Emitting Polymer: Polyfluorene-Containing Pendant Amino-Substituted Distyrylarylene Units†
Article first published online: 4 JUL 2005
Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Advanced Functional Materials
Volume 15, Issue 7, pages 1209–1216, July, 2005
How to Cite
Su, H.-J., Wu, F.-I., Tseng, Y.-H. and Shu, C.-F. (2005), Color Tuning of a Light-Emitting Polymer: Polyfluorene-Containing Pendant Amino-Substituted Distyrylarylene Units. Adv. Funct. Mater., 15: 1209–1216. doi: 10.1002/adfm.200400269
- Issue published online: 4 JUL 2005
- Article first published online: 4 JUL 2005
- Manuscript Accepted: 17 FEB 2005
- Manuscript Received: 21 JUN 2004
- Light-emitting diodes, organic (OLEDs);
We have synthesized a novel polyfluorene copolymer polyfluorene–bis[4-(diphenylamino)styryl]fluorene (PF–DPAS) by orthogonally attaching an amino-substituted distyrylarylene dye bis[4-(diphenylamino)styryl]fluorene, onto the C9 position of a fluorene unit. We have investigated this polymer's thermal properties, electronic properties (viz., absorption and photoluminescence), and electrochemical behavior. Photoluminescence studies indicate that color tuning can be achieved through efficient Förster energy transfer from the higher-energy polyfluorene backbone to the lower-energy pendant DPAS units. We have fabricated light-emitting diodes with the structure indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT)/emitting layer/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI)/Mg:Ag. The devices, based on blends of PF–DPAS in polyfluorene–triphenylamine–oxadiazole (PF–TPA–OXD), exhibit significant improvements in device performance relative to that of the pure PF–TPA–OXD device; we attributed this improvement to both a red-shift of the electroluminescence (EL) spectra and an enhancement in quantum efficiency. At a blend ratio of 1:20, the EL spectrum is voltage-independent and stable, and exhibits the characteristic emission of a DPAS moiety: a peak at 461 nm and Commission Internationale de l'Eclairage (CIE) coordinates of (0.15, 0.18). The maximum external quantum efficiency is 2.08 % (2.87 cd A–1) at a bias of 9 V (86.1 mA cm–2) with a brightness of 2467 cd m–2; the maximum brightness (6916 cd m–2) occurred at an applied voltage of 13 V and a current density of 361 mA cm–2.