New Design Tactics in OLEDs Using Functionalized 2-Phenylpyridine-Type Cyclometalates of Iridium(III) and Platinum(II)

As a result of their outstanding attributes, organic light-emitting diodes (OLEDs) and white organic light-emitting diodes (WOLEDs) have been recognized in recent years as the most promising candidates for future flat-panel display technologies and next generation solid-state energy-saving lighting sources. New advancements in the area of high performance triplet emitters become vital for realizing more practical applications. In this regard, several critical issues must be carefully identified and addressed, and these include the ways to enhance device efficiency and suppress efficiency roll-off, to achieve versatile color tuning and simple device manufacture, as well as to obtain high-quality white light from WOLEDs. It has been shown that some functionalized phosphorescent Ir-III and Pt-II ppy-type cyclometalated complexes (ppy=2-phenylpyridine) possess unique features that are suitable for solving these difficult and challenging tasks. In this Focus Review, we will highlight the recent design tactics adopted for these functional metallophosphors and the critical roles they may play in developing more realistic devices.