Near-infrared photoluminescence and electroluminescence of neodymium(III), erbium(III), and ytterbium(III) complexes

Tris(dibenzoylmethanato)(monobathophenanthroline)lanthanide(III) complex [Ln(DBM)(3) bath (Ln: Nd, Er and Yb)] both in solutions and thin films at room temperature showed narrow band photoluminescence (PL) due to the S-S transitions in the near-IR region: 890, 1070 and 1350 nm for Nd(III), 980 and 1540 nm for Er(III), and 985 nm for Yb(III). The PL efficiencies in solution were determined [phi (PL) = 3.3 x 10(-3) for Nd(III), 7.0 x 10(-5) for Er(III), and 1.4 x 10(2) for Yb(III)]. Organic electroluminescent (EL) devices having the structure of glass substrate/indium-tin oxide/N,N'-diphenyl-N.N'-di(m-tolyl)benzidine/ Ln(DBM)(3)bath(Ln: Nd, Er and Yb)/bathocuproine/Mg:Ag/Ag were fabricated, giving the EL bands around 900-1600 nm at room temperature. The external near-IR EL efficiencies at low current density were estimated by comparing with that of the Eu(III) device having the same structure. The saturation of near-IR EL intensity observed at the high current density suggested that the near-IR EL should suffer the T-T annihilation.