Synthesis of a high-efficiency red phosphorescent emitter for organic light-emitting diodes

Four novel red phosphorescent emitter compounds bis(1-phenylisoquinolinato-N, C^2′)iridium(acetylacetonate), (piq)₂Ir(acac), bis(1-(1′-naphthyl)isoquinolinato-N, C^2′)iridium(acetylacetonate), (1-niq)₂Ir(acac), bis(1-(2′-naphthyl)isoquinolinato-N, C^2′)iridium(acetylacetonate), (2-niq)₂Ir(acac) and bis(1-phenyl-5-methylisoquinolinato-N, C^2′)iridium(acetylacetonate), (m-piq)₂Ir(acac), have been synthesized and fully characterized. Electroluminescent devices with a configuration of ITO/NPB/CBP:dopant/BCP/AlQ₃/Al were fabricated. All devices emitted in the red region with an emission ranging from 624 to 680 nm. (m-piq)₂Ir(acac) shows a maximum brightness of 17 164 cd m^-2 at a current density of J= 300 mA cm^-2 and the best luminance efficiency of 8.91 cd A^-1 at a current density of J= 20 mA cm^-2. (1-niq)₂Ir(acac) exhibits pure-red emission with 1931 CIE (Commission International de L’Eclairage) chromaticity coordinates x= 0.701, y= 0.273.