A Phosphorescent Poly(dendrimer) Containing Iridium(III) Complexes: Synthesis and Light-Emitting Properties

• Published in: Macromolecules 2010-09, Vol.43 (17), p.6986-6994
• Main Authors: Lai, Wen-Yong, Levell, Jack W, Jackson, Andrew C, Lo, Shih-Chun, Bernhardt, Paul V, Samuel, Ifor D. W, Burn, Paul L
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Optoelectronic devices; Organic polymers; Physicochemistry of polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma101363h

A poly(styrene) with pendant dendronized iridium(III) complexes attached to every repeat unit was prepared in good yields using a free radical polymerization of a “macromonomer”. The dendronized pendant groups were heteroleptic iridium(III) complexes comprised of two 2-phenylpydridyl ligands, to which first generation biphenyl dendrons with 2-ethylhexyloxy surface groups were attached, and a phenyltriazolyl coligand that formed the attachment point to the polymer backbone. Dendronization of the pendant iridium(III) complexes was found to improve thermal stability, solubility, and solution (61%) and solid-state (13%) photoluminescence quantum yields (PLQYs) relative to the nondendronized homopolymer. Viscosity under normal solution processing conditions of 25 mg/mL was found to be 1.23 cSt. Importantly, although the phosphorescent iridium(III) chromophores are held closely along the polymer backbone, they do not significantly reduce the PLQY in solution by intrachain chromophore interactions. Simple bilayer organic light-emitting diodes comprising a blend of the poly(dendrimer) with 4,4-bis(N-carbazolyl)biphenyl and an electron transporting layer had good performance with an external quantum efficiency of 6.2% at 100 cd/m2.