Electrophosphorescent Chelating Copolymers Based on Linkage Isomers of Naphthylpyridine−Iridium Complexes with Fluorene

• Published in: Macromolecules Vol. 39; no. 5; pp. 1693 - 1700
• Main Authors: Zhen, Hongyu, Luo, Chan, Yang, Wei, Song, Wuyuan, Du, Bin, Jiang, Jiaxing, Jiang, Changyun, Zhang, Yong, Cao, Yong
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 07-03-2006
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Inorganic and organomineral polymers; Optoelectronic devices; Physicochemistry of polymers; Preparation; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Voltage current curve; Solution polycondensation; Polychelate; Organometallic copolymer; Photoluminescence; Iridium complex; Electroluminescence; Quantum yield; Suzuki coupling; Conjugated copolymer; Optical properties; Morphology; Preparation; Copolycondensation; Aromatic copolymer; Organic light emitting diodes; Pyridine derivative copolymer; Phosphorescence; Fluorene derivative copolymer; Optical absorption
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma052057h

A series of phosphorescent chelating copolymers based on the linkage isomers of 2-(1-naphthalene)pyridine− and 2-(2-naphthalene)pyridine−bicycloiridium complexes were synthesized by Suzuki polycondensation of A−A- and B−B-type monomers. These linkage isomers-based copolymers show distinct differences in their photophysical and electroluminescence properties. The phosphorescent emission band of the copolymer PF1−NpyIrm is in the region of 630 nm, whereas copolymers PF2−NpyIrm show an emission with the peak maximum at 590 nm, which are both red-shifted around 20 nm compared with the emissions of the pristine complexes. The highly efficient saturated red-phosphorescent PLEDs were achieved on the basis of copolymers PF1−NpyIrm. The best device performances are observed from copolymer PF1−NpyIrm1 with an external quantum efficiency (ηext) of 6.5% photon/electron (ph/el) at the current density of 38 mA/cm2, with the emission peak at 630 nm (x = 0.65, y = 0.31) and the luminance of 926 cd/m2. The efficiency remains as high as ηext = 5.3% ph/el at a high current density of 100 mA/cm2. No remarkable efficiency decay with the increase in current density shows that the chelating copolymers are promising candidate materials for phosphorescent polymer light-emitting diodes (PHPLEDs).