Iridium(iii) soft salts from dinuclear cationic and mononuclear anionic complexes for OLED devices

Abstract

Two iridium(III) soft salts based on ion-paired dinuclear cationic and mononuclear anionic complexes were designed and investigated as phosphorescent emitters for solution processed OLEDs. New dinuclear cationic complexes were prepared with two different bridging ligands, a carbazole and a phenylene spacer. Best devices were designed with the soft salt bearing a carbazole moiety.

Solution-processed blue phosphorescent OLEDs with carbazole-based polymeric host materials

“…Among all triplet emitters under investigations, iridium complexes have been identified as the most promising candidates as these organometallic complexes have high photoluminescence quantum yields at room temperature, relatively short excited state lifetimes and excellent color tunability [9]. So far, neutral [10][11][12][13][14], cationic [15][16][17][18], anionic [19][20] and even soft salts [21][22][23] where both the anionic and the cationic complex can contribute to light emission were successfully used as triplet emitters for electroluminescent devices.…”

Carbazole-based polymers as hosts for solution-processed organic light-emitting diodes: Simplicity, efficacy

“…Among all phosphors that have been investigated to date, iridium complexes have undoubtedly been the most widely studied. These complexes are highly versatile since neutral [7][8][9][10][11][12], cationic [13][14][15][16][17], anionic [18,19] but also soft salts [20,21], in which both the ion-paired anionic and cationic iridium complexes can participate to light emission, were successfully used as triplet emitters for OLEDs. These complexes also benefit from several appealing features including high quantum yield of luminescence [22,23], phosphorescence at room temperature [24] and relatively short excited state lifetimes so that key adverse factors such as triplet-triplet annihilation and back energy transfer from the guest to the host are strongly limited [25][26][27][28].…”

Wide bandgap iridium complexes varying by their ancillary ligands: Influence on their electroluminescence properties

“…Emission color of these complexes can also be easily tuned from blue [7] to red [8] by modifying the ligands in the coordination sphere of the metal cation. As other figure of merit, neutral [7,8], cationic [9], anionic [10] complexes or even soft salts [11][12][13] composed of an anionic and a cationic iridium complex that can both participate to light emission were successfully used as emitters for light-emitting devices. However, neutral complexes are largely preferred over iridium salts, use of neutral complexes avoiding the presence of mobile counter-ions within the active layer.…”