Highly Efficient Organic Light-Emitting Diodes with Phosphorescent Emitters Having High Quantum Yield and Horizontal Orientation of Transition Dipole Moments

摘要

Orientation of the transition dipole moments of an emitter is an important factor influencing the effective quantum efficiency and the outcoupling efficiency in OLEDs. Horizontally oriented dipoles result in higher outcoupling efficiency than vertically oriented dipoles. Not only fluorescent molecules but also some phosphorescent molecules were reported to have preferred horizontal orientation in OLEDs to improve the outcoupling efficiency over the limit set under the assumption of the isotropic or random orientation of the molecules. However, the factors influencing the orientation of the phosphorescent dyes in phosphorescent OLEDs have not been reported yet.