Synthesis and characterization of some 5-coordinated aluminum-8-hydroxyquinoline derivatives for OLED applications

Some new 8-hydroxyquinoline derivatives, 1,4-di(bis(8-hydroxyquinoline)aluminum-oxy)benzene, abbreviated as Alq(1), and 1,2-di(bis(8-hydroxyquinoline)aluminum-oxy)benzene, abbreviated as Alq(2), have been synthesized for organic light emitting diodes (OLEDs) applications. Complexes are thermally evaporable as well as highly soluble in common organic solvents. Bright green photoluminescence (PL) peak appeared in the range of 520–525 nm in solid and solution forms. OLEDs were successfully prepared via both the ways by physical vapor deposition and by spin coating of the complexes. The performance of devices prepared by physical vapor deposition, was compared with that of well-studied Alq3. The device based on Alq(1), showed the brightness of 1400 cd/m2 at 8 V, while only 602 cd/m2 was observed for the device based on Alq3 at the same applied voltage, when the devices were prepared in the identical conditions. Alq(1) device showed the maximum luminous efficiency of 0.94 cd/A at 0.1 A/cm2, while 0.75 cd/A at 0.1 A/cm2, was observed for Alq3 based device. A comparative characteristics study of the new complexes with that of Alq3 revealed that the new complexes are somewhat better than Alq3.