Molecular hosts for triplet emitters in organic light-emitting diodes and the corresponding working principle

This paper summarizes the mechanism and routes for excitation of triplet emitters in dopant emission based phosphorescent organic light-emitting diodes (PhOLEDs), providing a comprehensive overview of recent progress in molecular hosts for triplet emitters in PhOLEDs. Particularly, based on the nature of different hosts, e.g., hole transporting, electron transporting or bipolar materials, in which the dopant emitters can be hosted to generate phosphorescence, the respective device performances are summarized and compared. Highlights are given to the relationships among the molecular structure, thermal stability, triplet energy, carrier mobility, molecular orbital energy level and their corresponding device performances.