Infrared electroluminescence of ytterbium complexes in organic light emitting diodes

A comparison of near infrared (IR) emitting properties among Yb 3+ complexes containing devices was made. Ytterbium (dibenzoylmethanato) 3(bathophenanthroline) [Yb(DBM) 3bath] 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 2F 5/2→ 2F 7/2 electronic transition of the trivalent Yb ion, Yb 3+, was observed from the organic electroluminescent device. Current density dependence on drive voltage revealed good electron injection and transport properties of the Yb(DBM) 3 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.