Infrared and visible emission from organic electroluminescent devices based on praseodymium complex

Praseodymium(dibenzoylmethanato)(3)(bathophenanthroline) [Pr(DBM)(3)bath] was employed as an emitting and electron transport layer, and N,N-'-diphenyl-N,N-'-bis(3-methylphenyl)-1, 1(')-biphenyl-4,4(')-diamine (TPD) as a hole transport layer in organic electroluminescent (EL) devices. Bilayer device TPD/Pr(DBM)(3)bath and trilayer devices TPD/TPD:Pr(DBM)(3)bath/Pr(DBM)(3)bath with a different ratio of TPD to the Pr-complex were fabricated. Emission bands at 608 nm (D-1(2)--> H-3(6)), 890 nm (D-1(2)--> F-3(2)), 1015 nm (D-1(2)--> F-3(3)), 1065 nm (D-1(2)--> F-3(4)) and 1550 nm (D-1(2)--> (1)G(4)) originating from the internal f-f transitions of a Pr3+ ion were observed from EL devices using both bilayer and trilayer structures. Decreasing the ratio of TPD to the Pr-complex, the emission of the D-1(2)--> H-3(6) transition was promoted and that from the exciplex suppressed, which was explained in terms of energy transfer from the ligand to the central ion. (C) 2001 American Institute of Physics.