Effect of Smaller Counter Anion, BF₄^–, on the Electroluminescent Properties of Cationic Iridium Complex Based Light-Emitting Electrochemical Cells

Abstract

A cationic iridium complex with tetrafluoroborate (BF₄ ^-) as anion was synthesized and characterized for its potential application in display and solid state lighting devices. Light-emitting electrochemical cells (LECs) based on this complex displayed yellow electroluminescence with CIE coordinates of (0.50, 0.49). The imidazolium ionic liquids such as BMIMBF₄ and EMIMBF₄ were separately added to the light-emitting layer of the devices and their effects on the electroluminescent properties were studied. The presence of smaller BF₄ ^- ion effectively facilitates the charge injection from the electrodes and hence results in rapid increase of luminance and current density of the devices with voltages.

Keywords:

• Cationic iridium complex
• electrical properties
• light-emitting electrochemical cells
• thin films

Acknowledgments

This work was supported by the Basic Science Research Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Education, Science and Technology (NRF-2013R1A1A4A03009795) and the Brain Korea (BK) 21 Plus project.