Phenanthroimidazole as Molecularly Engineered Switch for Efficient and Highly Long-lived Light-Emitting Electrochemical Cell.

Abstract

Although, light-emitting electrochemical cells (LECs) based on Ir(III) complexes owing to the superior advantages exhibit high potential for display and lighting applications, they still suffer from relatively low stability and sluggish response time. To mitigate this challenge, herein, a series of Ir(III) complexes based on phenanthroimidazole (PI) as ancillary ligand were functionalized to achieve efficient, highly stable yellow to orange LEC devices with fast response. These complexes exhibit appropriate electrochemical stability and significant suppression of concentration quenching in the thin films compare to archetype complex. Concerning, the fabricated LECs showed remarkable long device lifetime over 1400 and 2100 hours and EQE of 2 and 3% for yellow and orange-LECs, respectively, in which obtained t1/2 for yellow LEC is among the highest value for cationic iridium (III) complexes based yellow-LECs reported so far. Subsequently, incorporation of ionic tethered functional group on PI, improved the mobility of emissive layer, reducing the device turn-on time around 75–88%. This study represents facile functionalization and characterization of PI ligand and its potential application in optoelectronic devices (OLED).