Saturated deep blue organic electrophosphorescence using a fluorine-free emitter

We demonstrate saturated, deep blue organic electrophosphorescence using the facial- and meridianal- isomers of the fluorine-free emitter tris(phenyl-methyl-benzimidazolyl)iridium(III)($f\text{-}\mathrm{Ir}{\left(\mathrm{pmb}\right)}_3$ and $m\text{-}\mathrm{Ir}{\left(\mathrm{pmb}\right)}_3$ , respectively) doped into the wide energy gap host, $p$ -bis(triphenylsilyly)benzene (UGH2). The highest energy electrophosphorescent transition occurs at a wavelength of $\lambda =389\mathrm{nm}$ for the fac- isomer and $\lambda =395\mathrm{nm}$ for the mer- isomer. The emission chromaticity is characterized by Commission Internationale de l’Eclairage coordinates of $(x=0.17,y=0.06)$ for both isomers. Peak quantum and power efficiencies of $(2.6\pm 0.3)\%$ and $(0.5\pm 0.1)\mathrm{lm}∕\mathrm{W}$ and $(5.8\pm 0.6)\%$ and $(1.7\pm 0.2)\mathrm{lm}∕\mathrm{W}$ are obtained using $f\text{-}\mathrm{Ir}{\left(\mathrm{pmb}\right)}_3$ and$m\text{-}\mathrm{Ir}{\left(\mathrm{pmb}\right)}_3$ respectively. This work represents a departure from previously explored, fluorinated blue phosphors, and demonstrates an efficient deep blue/near ultraviolet electrophosphorescent device.