Polynorbornene Copolymer with Side-Chain Iridium(III) Emitters and Carbazole Hosts: A Single Emissive Layer Material for Highly Efficient Electrophosphorescent Devices

• Published in: Macromolecules 2013-02, Vol.46 (3), p.674-682
• Main Authors: Park, Jun Ha, Koh, Tae-Wook, Chung, Jin, Park, Sung Hoon, Eo, Maengsun, Do, Youngkyu, Yoo, Seunghyup, Lee, Min Hyung
• Format: Article
• Language: English
• 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
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma302342p

Vinyl addition copolymerization of norbornene monomers using a Pd(II) catalyst in combination with 1-octene chain transfer agent efficiently produces well-defined soluble polynorbornene copolymers bearing side-chain (C∧N)2Ir(O∧O) emitters (C∧N = 2-(4,6-difluorophenyl)-pyridine (M 3 ); 2-phenyl-pyridine (M 4 ); 2-(benzo[b]thiophen-2-yl)-pyridine (M 5 ), O∧O = acetylacetonato) and 9,9′-(1,3-phenylene)bis-9H-carbazole (mCP) or 9,9′-(1,1′-biphenyl)-4,4′-diylbis-9H-carbazole (CBP) host moieties (M 1 and M 2 ). The catalytic system provides high-molecular-weight copolymers (M w = 151 000–457 000 g/mol) with a controlled incorporation of monomers. All copolymers possess high thermal stability with high decomposition (T d5 > 400 °C) and glass transition temperatures (T g > 330 °C). Among the solution-processed devices fabricated based on a single emissive layer comprising the blue-, green-, and red-phosphorescent copolymers (PBn, PGn, and PRn, n = 1–4) with various concentrations of emitters (1.7–13.9 mol %-Ir), the devices based on PB4 (10.5 mol %-Ir), PG2 (5.3 mol %-Ir), and PR4 (13.9 mol %-Ir) display the best performances with maximum power efficiencies of 12.9, 25.6, and 3.3 lm/W and maximum external quantum efficiencies of 8.8, 13.3, and 5.1%, respectively, for each color. These results correspond to almost double the efficiencies of the corresponding doped polymer systems and are outstanding among the polymeric rivals reported thus far.