A series of bis-cyclometalated iridium complexes, iridium(III) bis(2-(2,4-difluoro)phenylpyridine- N,C2') 3-acetyl camphor [(46dfppy)₂Ir(acam)], iridium(III) bis(2-phenylpyridinato-N,C2') 3-acetyl camphor [(ppy)₂Ir(acam)] and iridium(III) bis(2-(2'-benzothienyl) pyridinato-N,C3') 3-acetyl camphor [(btp)₂Ir(acam)] were synthesized with sterically 3-acetyl camphor as ancillary ligand. The absorption spectrum, PL spectra and photoluminescence efficiency of complexes were compared with the corresponding complexes with acetylacetone (acac) as the ancillary ligand. It was found that all of their photoluminescence efficiency could be improved when sterically hindered 3-acetyl camphor was introduced. When [(ppy)₂Ir(acam)] was used as light-emitting devices, the EL spectra has the largest peak intensity at 516 nm. The device has the greatest brightness of 10930 cd/m² and maximum brightness efficiency of 14.6 cd/A at 12 V. The highest power effciency and brightness are 4.23 lm/W and 698 cd/m² respectively at 10.7 V.

Key words: bis-cyclometalated iridium complexes, 3-acetyl camphor, quantum efficiency