Efficient yellow-green organic light-emitting diodes based on sublimable cationic iridium complexes

• Sublimable cationic iridium complexes.
• Bis-carbazole substituted 4,5-diazafluorene ligand.
• Yellow-green organic light-emitting diodes.

Three new yellow-emitting cationic iridium complexes have been prepared, and the photophysical and electrochemical properties have been investigated. These cationic iridium complexes have excellent thermal stability and can be thermally vacuum-sublimed as phosphorescent dyes for the fabrication of efficient organic light-emitting diodes. The devices based on these complexes give yellow-green electroluminescences with Commission Internationale de L'Eclairage coordinates of (0.38, 0.58), (0.37, 0.58), (0.38, 0.58). The maximum current efficiencies of devices based on these complexes are 20.2, 23.7 and 21.5 cd A−1 that corresponds to maximum external quantum efficiencies of 6.3%, 6.8% and 6.5%, respectively.

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