Anthracene-Based Organic Small-Molecule Electron-Injecting Material for Inverted Organic Light-Emitting Diodes

A diphenylanthracene dimethylamine derivative (9-{3,5-di(N,N-dimethylaminoethoxy)phenyl}-10-phenyl-anthracene, DPAMA) was synthesized by the Suzuki–Miyaura cross-coupling reaction. Its ammonium salt, 9-{3,5-di(trimethylammonium ethoxy)phenyl}-10-phenyl-anthracene dichloride (DPAMA-Cl), was also synthesized as a reference material. DPAMA was characterized by UV–vis and fluorescence spectroscopy, cyclic voltammetry, photoelectron yield spectroscopy, and X-ray photoelectron spectroscopy to evaluate the work function-modifying ability of DPAMA on indium tin oxide (ITO) and ZnO. The work functions of ITO and ZnO changed from 4.4 and 4.0 eV (pristine) to 3.8 and 3.9 eV, respectively. Using this surface modification effect of DPAMA, inverted organic light-emitting diodes were fabricated with device structures of ITO/DPAMA/Alq3/NPD/MoO3/Al (Alq3 = tris(8-hydroxyquinolinato)aluminum; NPD = N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-(biphenyl)-4,4′-diamine) and ITO/ZnO/DPAMA/Alq3/NPD/MoO3/Al. Both devices showed goo...