Fluorenylpyridine-derived iridium complexes for electrophosphorescent light-emitting diodes.

To develop efficient emitting materials for organic light-emitting diodes (OLEDs), a series of cyclometalated iridium complexes with 2-fluorenylpyridine-derived ligands were synthesized. Complexes 1-4 exhibited yellow to red phosphorescence with quantum yields of 0.17-0.33 in degassed CH2Cl2. Multilayered OLEDs were fabricated by using these iridium complexes as dopant materials. In the device employing complex 1 as a dopant, the maximum luminance, maximum luminance efficiency and maximum power efficiency were 15600 cd/m2 at 14 V, 12.8 cd/A, and 8.94 Im/W, respectively, at the CIE coordinates of (0.648, 0.350), which is close to the saturated red emission. The electron-withdrawing carbonyl substituent groups affected markedly the EL performances of fluorenylpyridine-derived iridium complexes as red emitting materials.