Rational Design of Ir(III) Phosphors to Strategically Manage Charge Recombination for High-Performance White Organic Light-Emitting Diodes.

Constructing high-quality white organic light-emitting diodes (WOLEDs) remains a big challenge because of high demands on the electroluminescence (EL) performance including high efficiency, excellent spectral stability, and low roll-off simultaneously. To achieve effective energy transfer and trap-assisted recombination in the emissive layer, herein, four Ir(III) phosphors, namely, m OMe-Ir-PI ( 1 ), p OMe-Ir-PI ( 2 ), m OMe-Ir-PB ( 3 ), and p OMe-Ir-PB ( 4 ), were strategically designed via simple regulation of the substituent moiety and π conjugation of the chelated ligands. Their photophysical and EL properties were systematically investigated. When these phosphors are employed as doped emitters, the monochromic green organic light-emitting diodes not only exhibit a superior performance with the characteristics of 50.2 cd A -1 , 39.2 lm W -1 , and 15.1%, but also maintain a negligible roll-off ratio of 0.2% at 1000 cd m -2 , which are better than those of commercial green Ir(ppy) 2 acac and Ir(ppy) 3 in the same device configuration. Inspired by these outstanding performances, we successfully fabricated the warm WOLED utilizing 2 as a green component, affording a peak efficiency of 42.0 cd A -1 , 29.3 lm W -1 , and 18.6% and retaining at 39.9 cd A -1 , 23.7 lm W -1 , and 17.4% even at 1000 cd m -2 . The results herein demonstrate the superiority of the molecular design and propose a simple method toward the development of promising Ir(III) phosphors for high-efficiency WOLEDs.