Infrared electroluminescence of ytterbium complexes in organic light emitting diodes

A comparison of near infrared (IR) emitting properties among Yb3+ complexes containing devices was made. Ytterbium (dibenzoylmethanato)(3)(bathophenanthroline) [Yb(DBM)(3)bath] was used as electron-transport and emitting material. N,N ' -diphenyl-N, N ' -bis(3-methylphenyl)-1,1 ' -biphenyl-4,4 ' -diamine (TPD) acted as a hole-transport layer. Utilizing a device of trilayer structure ITO/TPD (40 nm)/Yb(DBM)(3) bath: TPD (weight ratio approx. 1:1, 40 nm)/Yb(DBM)(3) bath (80 nm)/Ag:Mg (150 nm), an intense emission corresponding to the F-2(5/2) --> F-2(7/2) electronic transition of the trivalent Yb ion, Yb3+, was observed from the organic electroluminescent device. Current density dependence on drive voltage revealed good electron injection and transport properties of the Yb(DBM), bath. The tendency of the efficiencies of IR and visible emissions under different current densities was discussed. A broad band at approximately 580 nm was observed in the EL spectrum, which could be assigned to exciplex emission. (C) 2001 Elsevier Science B.V. Ah rights reserved.