5-Isobutyryl-2-phenylpyridine-derived iridium complexes for red phosphorescent light-emitting diodes

For the development of efficient red materials in organic light emitting diodes, a series of cyclometalated iridium complexes with 5-isobutyryl-2-arylpyridine-derived ligands were synthesized. Complexes 1-4 exhibited red phosphorescence with quantum yields of 0.16-0.48 in degassed CH2Cl2. An OLED device employing iridium complex 3 as a dopant exhibited the best performance with a maximum luminance of 35500 cd/m2 at 14 V and luminance and power efficiencies of 15.5 cd/A and 6.23 Im/W at 20 mA/cm2, respectively. In the device employing complex 2 as the dopant, the maximum luminance was 6300 cd/m2 at 14 V and the maximum luminance efficiency and power efficiencies were 5.23 cd/A and 3.16 Im/W at 5.2 V, respectively, with CIE coordinates of (0.66, 0.32) at 9.0 V, close to the saturated red emission.