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

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) 2 Ir(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-9 H -carbazole (mCP) or 9,9′-(1,1′-biphenyl)-4,4′-diylbis-9 H -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.