Solution-Processable Csp³‑Annulated Hosts for High-Efficiency Deep Red Phosphorescent OLEDs

In this report, a solution-processable cohost system incorporating N,N′-di­(naphtalene-1-yl)-N,N′-diphenylbenzidine (NPB) and Csp³-annulated phenylquinoline derivatives, including spiro­[indeno­[1,2-b]­quinoline-11,8′-indolo­[3,2,1-de]­acridine] (IAIQ), 10-phenyl-10H-spiro­[acridine-9,11′-indeno­[1,2-b]­quinoline] (PAIQ) and 3,3′-(11H-indeno­[1,2-b]­quinoline-11,11-diyl)­bis­(N-phenyl-N-(m-tolyl)­aniline) (m-TPA-DPIQ), is developed for highly efficient saturated red phosphorescent organic light emitting diodes (OLEDs). IAIQ, PAIQ, and m-TPA-DPIQ, designed with the increase of molecular flexibility, are systematically investigated. Solution-processable devices based on the efficient phosphorescent emitter bis­[2-(3,5-dimethylphenyl)­isoquinolinato]­(2,8-dimethyl-4,6-nonanedionato)­Iridium [Ir­(mpiq)₂divm] are successfully fabricated, and give electroluminescent peaks at 634–636 nm with Commission Internationale de L’Eclairage coordinates of (0.70, 0.30). Under optimized conditions, the devices incorporating IAIQ, PAIQ, and m-TPA-DPIQ exhibit high external quantum efficiency with the maximum value at 25.1%, 23.4%, and 23.3%, respectively, and all exceeding 18% at the luminance of 1000 cd/m². In application, the supersaturated red devices with excellent performance could facilitate the development of wet-made displays. The newly developed Csp³-annulated host materials with their excitonic properties also showoff the tactic to construct cohost system for high-quality phosphorescent OLEDs.