100% phosphorescence quantum efficiency of Ir(III) complexes in organic semiconductor films

We demonstrate that three Ir(III) complexes used as principal dopants in organic electrophosphorescent diodes have very high photoluminescence quantum efficiency (eta(PL)) in a solid-state film. The green emitting complex, fac-tris(2-phenylpyridinato)iridium(III) [Ir(ppy)(3)], the red-emitting bis[2-(2'-benzothienyl)pyridinato-N,C-3'] (acetylacetonato)iridium(III) [Btp(2)Ir(acac)], and the blue complex bis[(4,6-difluorophenyl)pyridinato-N, C-2](picolinato)iridium(III) (FIrpic) were prepared as codeposited films of varying concentration with 4,4'-bis(N-carbazolyl)-2, 2'-biphenyl, a commonly used host material. The maximum eta(PL) values for Ir(ppy)3, Btp(2)Ir(acac), and FIrpic were, respectively, 97% +/- 2% (at 1.5 mol%), 51% +/- 1% (at 1.4 mol%), and 78% +/- 1% (at 15 mol%). Furthermore, we also observed that the maximum eta(PL) of FIrpic reached 99% +/- 1% when doped into the high triplet energy host, m-bis(N-carbazolyl)benzene, at an optimal concentration of 1.2 mol%. (C) 2005 American Institute of Physics.