Iridium(III) Complexes for OLED Application

This chapter focuses on Iridium(III) complexes for organic light-emitting diode (OLED) applications and gives a general introduction to metal complexes and OLED devices, and then describes selected examples, to illustrate the tunability of the emission energies. The iridium complexes will be organized by emission colors and therefore divided in green, red, and blue emissive materials. Most of the Ir(III) complexes used in OLEDs are based on homoleptic triscyclometalated Ir(III), Ir(C^N)3, or neutral heteroleptic bis-cyclometalated [Ir(C^N)2(L^X)] complexes. Among all the transition metal complexes, iridium(III) complexes are considered the most studied for optoelectronic applications. The host material with the phosphorescent emitter is very critical for achieving high efficiency in phosphorescent OLEDs (PHOLEDs). During the operation of the device, the phosphorescent emitters in the doped emissive layer (EML) are electrically excited to generate the electrophosphorescence by either host-guest energy transfer (ET) or direct charge carrier trapping.