Organic light-emitting diodes using novel metal–chelate complexes

Electroluminescent (EL) properties of novel metal–chelate complexes have been investigated in the organic light-emitting diodes (OLEDs) comprised of the hole transport layer (HTL) and emitting layer (EML). The metal–chelate complexes have either polycyclic aromatic or fused ring ligands, which coordinate to zinc or aluminum. Various EL emission colors over the range of blue to yellow were obtained. The OLEDs using the complexes with polycyclic aromatic ligands showed desirable blue emission with a quantum efficiency of 1.5–1.7% at a luminance of 300 cd/m2 and CIE color coordinates of around (0.17, 0.16). By perylene-doping into the blue-emitting complex, the improvement of EL efficiency was observed. On the other hand, the complex with fused ring ligands gave a quantum efficiency of 0.8% at yellow emission.