Highly Efficient Multifluorenyl Host Materials with Unsymmetrical Molecular Configurations and Localized Triplet States for Green and Red Phosphorescent Devices

摘要

The controllable modulation of the optoelectronic properties of the host materials in phosphorescent organic light-emitting diodes (PHOLEDs) has been one of the most fundamental issues and most significant challenges for PHOLEDs; the challenge remains even after a flourish of developments in electro-phosphorescence over the past few decades,where host matrices with favorable electroactivity and suitable excited energy have been employed to confine triplet excitons on dopants and to suppress triplet-involved quenching effects, such as triplet-triplet annihilation (TTA) and (triplet exciton)-polaron quenching (TPQ).Because approaches to decreasing TTA and TPQ through device optimization are rather limited and these quenching mechanisms mainly occur in the bulk of emitting layers (EMLs) with the predominant participation of excited and/or charged host molecules, efforts toward the development of hosts with desired optoelectronic properties are logical and promising.