Not All Bis[2-(4,6-difluorophenyl)pyridyl-N,C2′]iridium(III) Picolinate (Flrpic) Isomers Are Unsuitable for Developing Long-Lifetime Blue Phosphorescent Organic Light-Emitting Diodes

Bis[2-(4,6-difluorophenyl)pyridyl-N,C2']iridium(III) picolinate (Flrpic) is the most widely used blue phosphorescent material for PhOLEDs, but its stability is generally considered insufficient for practical applications. To understand its insufficient stability further, we evaluated the degradation mechanism of Flrpic isomers in different electronic states (i.e., ground, anion, cation, lowest singlet, and triplet excited states). We developed a theoretical method to identify the degradation lifetime of Flrpic in PhOLEDs. Finally, we found that the extremely short lifetime of Flrpic-based PhOLEDs is mainly caused by two of its four isomers, while one of its other isomers exhibited high stability. Our findings demonstrated that not all Flrpic isomers are unstable for the development of long-lifetime PhOLEDs. We propose to achieve the practical application of highly efficient and long-lifetime blue PhOLEDs by isolating the high-stability isomer of Flrpic from the others. This will accelerate the application of PhOLEDs in the field of display and white-light illumination.