Cyclometalated Ir complexes in polymer organic light-emitting devices

Several new iridium based cyclometalated complexes were investigated as phosphorescent dopants for molecularly doped polymeric organic light-emitting diodes. Specifically, the complexes used in this study were iridium (III) $\mathrm{bis}\text{(2-}\mathrm{phenylpyridinato}{\mathrm{-N,C}}^{2^{\prime }})$ (acetylacetonate) [ppy], iridium (III) $\mathrm{bis}\text{(7,8-}\mathrm{benzoquinolinato}{\mathrm{-N,C}}^{3^{\prime }})$ (acetylacetonate) [bzq], iridium (III) $\mathrm{bis}\text{(2-}\mathrm{phenylbenzothiazolato}{\mathrm{-N,C}}^{2^{\prime }})$ (acetylacetonate) [bt], iridium (III) $\mathrm{bis}{\text{(2-(2}}^{\prime }-\mathrm{naphthyl})\mathrm{benzothiazolato}{\mathrm{-N,C}}^{2^{\prime }})$ (acetylacetonate) [bsn] and iridium (III) $\mathrm{bis}{\text{(2-(2}}^{\prime }-\mathrm{benzo}\text{[4,5-}\mathrm{a}]\mathrm{thienyl})\mathrm{pyridinato}{\mathrm{-N,C}}^{3^{\prime }})$ (acetylacetonate) [btp]. Single layer devices of doped polyvinylcarbazole: 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole give maximum external quantum efficiencies that varied from 3.5% for the ppy dopant to 0.4% for the btp dopant. Several different device heterostructure architectures were explored, and the best quantum efficiency of the devices reached 4.2% for the heterostructures.