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 (ηPL) in a solid-state film. The green emitting complex, fac-tris(2-phenylpyridinato)iridium(III) Ir(ppy)3, the red-emitting bis2-(2′-benzothienyl)pyridinato-N,C3′ (acetylacetonato)iridium(III) Btp2Ir(acac), and the blue complex bis(4,6-difluorophenyl)pyridinato-N,C2(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 ηPL values for Ir(ppy)3, Btp2Ir(acac), and FIrpic were, respectively, 97%±2% (at 1.5mol%), 51%±1% (at 1.4mol%), and 78%±1% (at 15mol%). Furthermore, we also observed that the maximum ηPL of FIrpic reached 99%±1% when doped into the high triplet energy host, m-bis(N-carbazolyl)benzene, at an optimal concentration of 1.2mol%.