The counter anion effect of ion-type phosphorescent dye tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) complexes as dopant for light-emitting diodes

► The counter anion effect of RuII complex on photophysical properties was studied. ► RuII complex with large anion performs better in doped OLEDs. ► The counter anion has the effect on dominant mechanism in the doped OLEDs. ► Providing an easy way to get appropriate dye for diodes with better performance.