Iridium(III) Complexes Bearing Quinoxaline Ligands with Efficient Red Luminescence Properties

Newly designed cyclometalated iridium(III) complexes bearing 2,3-diphenylquinoxalines, which were shown to be highly efficient and pure-red emitting materials for electrophosphorescent organic light-emitting diodes (OLEDs), were synthesized and characterized. Excellent quantum efficiencies for photoluminescence within the range of 50-79% were attained in dichloromethane solution at room temperature. Luminescence peak wavelengths of the complexes were within the preferred range of 653-671 nm in thin films. The most vivid red electrophosphorescence with CIE chromaticity coordinates x = 0.70 and y = 0.28, which are the closest to the ultimate limit of pure red among reported OLEDs, was achieved with the acetylacetonatoiridium complex bearing 2,3-diphenylquinoxaline.