Cationic iridium(III) complexes with different-sized negative counter-ions for solution-processed deep-blue-emitting diodes

Abstract

A series of blue-emitting cationic iridium(III) complexes featuring the same coordinated iridium(III) cation while different-sized negative counter-ions are reported and investigated. Anionic influence on the physicochemical properties and device performance is studied and explained. Introduction of counter-ions with large steric hindrance, (i) effectively reduces the ionic interaction and molecular aggregation in solid states, improving the photoluminescence efficiency and avoiding the common bathochromic shift; (ii) also restricts anionic drift under the working bias in the optoelectronic devices, achieving solution-processed deep-blue-emitting diodes with a major peak at only 452 nm, among the shortest emission wavelengths of devices based on ionic transition metal complexes.