Iridium-based light-emitting electrochemical cells containing ionic liquids in the luminous layer

To fabricate transition metal complex-based LECs (light-emitting electrochemical cells), ([Ir(ppy)2(5,6-dime-1,10-phenthroline)]PF6 was synthesized and used as a luminous material and ILs (ionic liquids) were incorporated into a luminous layer, in which two types of ionic liquid were used; 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). ILs were added to a [Ir(ppy)2(5,6-dime-1,10-phenthroline)]PF6 luminous layer to improve ionic conductivity and light intensity. Both ILs significantly increased the current density and luminance. Due to the small molecule of BF4−, turn-on time was reduced and ionic conductivity was increased. However, the device stability was sacrificed. High current efficiency of 34.5 cd/A was investigated at 7 V of BMIMPF6-doped luminous layer. The LECs based on [Ir(ppy)2(5,6-dime-1,10-phenthroline)]PF6 gave yellow emission color when ILs were added into light-emitting layer, and no significant change of color has been found in this study.