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

We demonstrate that three $\mathrm{Ir}\left(\mathrm{III}\right)$ complexes used as principal dopants in organic electrophosphorescent diodes have very high photoluminescence quantum efficiency $\left({\eta }_{\mathrm{PL}}\right)$ in a solid-state film. The green emitting complex, fac-tris(2-phenylpyridinato)iridium(III) $\left[\mathrm{Ir}{\left(\mathrm{ppy}\right)}_3\right]$ , the red-emitting $\mathrm{bis}\left[2\text{-}\left(2^{\prime }\text{-}\text{benzothienyl}\right)\text{pyridinato}\text{-}\mathrm{N},{\mathrm{C}}^{3\prime }\right]$ (acetylacetonato)iridium(III) $\left[{\mathrm{Btp}}_2\mathrm{Ir}\left(\mathrm{acac}\right)\right]$ , and the blue complex $\mathrm{bis}\left[\left(4,6\text{-}\text{difluorophenyl}\right)\text{pyridinato}\text{-}\mathrm{N},{\mathrm{C}}^2\right]\left(\text{picolinato}\right)\text{iridium}\left(\mathrm{III}\right)$ $\left(\text{FIrpic}\right)$ were prepared as codeposited films of varying concentration with $4,4^{\prime }\text{-}\mathrm{bis}\left(N\text{-}\text{carbazolyl}\right)\text{-}2,2^{\prime }\text{-}\text{biphenyl}$ , a commonly used host material. The maximum ${\eta }_{\mathrm{PL}}$ values for $\mathrm{Ir}{\left(\mathrm{ppy}\right)}_3$ , ${\mathrm{Btp}}_2\mathrm{Ir}\left(\mathrm{acac}\right)$ , and $\text{FIrpic}$ were, respectively, $97\%\pm 2\%$ (at $1.5\mathrm{mol}\%$ ), $51\%\pm 1\%$ (at $1.4\mathrm{mol}\%$ ), and $78\%\pm 1\%$ (at $15\mathrm{mol}\%$ ). Furthermore, we also observed that the maximum ${\eta }_{\mathrm{PL}}$ of $\text{FIrpic}$ reached $99\%\pm 1\%$ when doped into the high triplet energy host, $m\text{-}\mathrm{bis}\left(N\text{-}\text{carbazolyl}\right)\text{benzene}$ , at an optimal concentration of $1.2\mathrm{mol}\%$ .