High-Efficiency Organic Light-Emitting Diodes Based on Sublimable Cationic Iridium(III) Complexes with Sterically Hindered Spacers

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.