1.1 μm near-infrared electrophosphorescence from organic light-emitting diodes based on copper phthalocyanine

We demonstrated near-infrared organic light-emitting devices employing copper phthalocyanine (CuPc) doped into 4,4(')-N,N-'-dicarbazole-biphenyl (CBP). Room-temperature electrophos-phorescence was observed at about 1.1 mu m due to transitions from the first excited triplet state to the singlet ground state (T-1-S-0) of CuPc. There existed very weak emission of CBP from undoped devices, and at lower doping concentrations (<= 12 wt %) the driving voltages of doped devices were higher than that of undoped devices. The results indicated that Forster [Ann. Physik. (Leipzig) 2, 55 (1948)] and Dexter [J. Chem. Phys. 21, 836 (1953)] energy transfers play a minor role in these devices, and direct charge trapping appears to be the dominant mechanism. (c) 2006 American Institute of Physics.