Two novel orange cationic iridium(III) complexes with multifunctional ancillary ligands used for polymer light-emitting diodes

Two novel orange cationic iridium complexes [(npy)(2)Ir(o-phen)]PF6 and [(npy)(2)Ir(c-phen)] PF6 were synthesized. Hnpy: 2-(naphthalen-1-yl) pyridine; o-phen: a 1,10-phenanthroline derivative containing an electron-transporting functional group of 2,5-diphenyl-1,3,4-oxadiazole and a crystallization-resistant tert-butyl functional group; c-phen: a 1,10-phenanthroline derivative containing a hole-transporting functional group of carbazole and a crystallization-resistant 2-ethylhexyl functional group. Both of them are amorphous and possess high thermal stability with 5% weight-reduction temperatures (Delta T-5%) of 386 degrees C and 383 degrees C, and glass-transition temperatures (T-g) of 267 degrees C and 195 degrees C respectively. They were used as phosphorescent dopants in polymer light-emitting diodes (PLEDs) fabricated by solution-processed technology with configuration of ITO/PEDOT:PSS/PVK:PBD:iridium complex/TPBI/CsF/Al. At the optimal doping concentration of 2.0 wt%, the corresponding PLEDs exhibited the maximum current efficiencies of 9.1 cd A(-1) and 10.0 cd A(-1), the maximum external quantum efficiencies of 6.5% and 7.1%, and the maximum luminance of 2314 cd m(-2) and 3157 cd m(-2) respectively, with the same CIE coordinates of (0.57, 0.40). The results indicate that cationic iridium complexes are promising candidates for PLED applications when they are designed reasonably. (C) 2012 Elsevier B.V. All rights reserved.