Recent Progress of Iridium(III) Red Phosphors for Phosphorescent Organic Light-Emitting Diodes

This chapter provides a survey of red iridium (III) phosphorescent materials that has been used in red organic light-emitting diodes (OLEDs) in the past few years. Their structure-efficiency relationship and photophysical and electroluminescence properties are discussed. Functionalization of Ir(III) cyclometalated complex with suitable ligand can afford red dopant with remarkable photophysical, thermal, and electroluminescence (EL) properties. The molecular ligand structure of the Ir(III) complex is critical in tuning the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of a red dopant, which in turn affects the energy difference between the host and the energies of these frontier orbitals of the dopant that has a great influence on the efficiency of the final red-emitting device. An insight into the structure-efficiency relationship of these Ir(III) cyclometalated complexes is clearly important for the future development of new high-performance red phosphorescent emitters.