A Novel Linking Strategy of Using 9,10‐Dihydroacridine to Construct Efficient Host Materials for Red Phosphorescent Organic Light‐Emitting Diodes

Abstract

Abstract Three novel 9,10‐dihydroacridine derivatives, 4′‐(10‐methyl‐9,9‐diphenyl‐9,10‐dihydroacridin‐4‐yl)[1,1′‐biphenyl]‐4‐carbonitrile (MeAcPhCN), 4′‐(9,9,10‐triphenyl‐9,10‐dihydroacridin‐4‐yl)[1,1′‐biphenyl]‐4‐carbonitrile (PhAcPhCN), and 5‐[4‐(9,9,10‐triphenyl‐9,10‐dihydroacridin‐4‐yl)phenyl]picolinonitrile (MeAcPyCN), were prepared by the attachment of [1,1′‐biphenyl]‐4‐carbonitrile or 5‐phenylpicolinonitrile to the 4‐position of 9,10‐dihydroacridine. This special linking strategy limited the conjugation length, maintained the triplet energy, and inhibited the intermolecular charge‐transfer (ICT) characteristics of these compounds. Notably, the enhanced accepting strength of the picolinonitrile segment relative to that of benzonitrile led to relatively strong ICT characteristics, a low energy gap, and a low triplet energy for MeAcPyCN. The thermal, photophysical, electrochemical, and electroluminescent properties of these host materials were studied systematically. Consequently, (acetylacetonato)bis(2‐methyldibenzo[ f , h ]quinoxaline)iridium(III) [Ir(MDQ) 2 (acac)]‐based red phosphorescent organic light‐emitting diodes (PHOLEDs) were fabricated with these three host materials. As a result, the device hosted by MeAcPhCN showed good device performance with a maximum external quantum efficiency of 20.5 %.