Electrochemistry and Electrogenerated Chemiluminescence Processes of the Components of Aluminum Quinolate/Triarylamine, and Related Organic Light-Emitting Diodes

Solution electrochemical studies have been conducted of the principle lumophores, dopants, and hole-transport agents of aluminum-quinolate(Alq3)-based organic light-emitting diodes (OLEDs) along with the characterization of their electrogenerated chemiluminescence (ECL). In acetonitrile/benzene solvent mixtures, Alq3 shows single one-electron reduction and oxidation processes, with a separation between the first oxidation and first reduction potentials, ΔEelectrochemical = 3.03 V, close to the estimates of energy difference between HOMO and LUMO levels obtained from absorbance spectra of thin films of Alq3, ΔEoptical = 3.17 eV. A new sulfonamide derivative of Alq3, (Al(qs)3), showed a positive shift (ca. 0.32 V) in the first reduction potential versus the parent molecule, and resolution of the overall reduction process into three successive, chemically reversible, one-electron reductions. Two successive one-electron oxidations are seen for 4,4‘-bis(m-tolyphenylamino)biphenyl (TPD), a hole-transporting mat...