Effect of the ligand on the properties of emitting materials: Pentacoordinated 8-hydroxyquinoline aluminum complexes

Two series of pentacoordinated complexes, AlMq2q′ and Alq2q′ (q is 8-hydroxyquinoline, Mq is 2-methyl-8-hydroxyquinoline and q′ is phenolato ligand), were synthesized, and assessed as potential emitting materials in thin film (photoluminescence, PL) and electroluminescent (EL) device. EL devices with a configuration of ITO/NPB(50 nm)/Complex(50 nm)/Mg/Ag(10:1) were fabricated. Strong blue and green emission were observed from thin solid film and EL device of AlMq2q′ and Alq2q′, respectively. The results revealed that the PL and EL emission wavelengths of these materials are primarily determined by Mq and q (first ligand), whereas phenolato ligand (second ligand) has little effect on the emission wavelength but remarkable influence on EL efficiency.