High-Efficiency Organic Light-Emitting Diodes Based on Sublimable Cationic Iridium(III) Complexes with Sterically Hindered Spacers
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Cationic iridium(III) complexes show great promise as phosphorescent materials, while their utilization in organic light-emitting diodes is severely hindered by the inferior sublimability and low device performance. Here we devise a judicious strategy to develop high-efficiency sublimable cationic iridium(III) complexes by simultaneously introducing sterically hindered spacers into the negative counterions, major and ancillary ligands. We have exploited a novel series of yellow and red emitters, investigated their photophysical properties, electrochemical behaviors, and thermal stabilities, and finally fabricated organic light-emitting diodes by vacuum evaporation deposition. Record-high device performance has been achieved with a superior external quantum efficiency of 16%, excellent power efficiency of 49 lm/W, maximum brightness over 27.3 × 103 cd/m2, very low turn-on voltage below 2.5 V, and quite small efficiency roll-off. Our study represents a significant advance in the development of sublimable cationic iridium(III) complexes and evidences their promising applications in state-of-the-art optoelectronic devices.
