Toward High‐Performance Vacuum‐Deposited OLEDs: Sublimable Cationic Iridium(III) Complexes with Yellow and Orange Electroluminescence

Abstract Great advances in the development of efficient luminescent materials are the driving force behind organic light‐emitting diodes (OLEDs). Sublimable ionic transition‐metal complexes (iTMCs) have emerged as a large family of new emissive dopants applied for vacuum‐deposited OLEDs, while the achievement of excellent performance remains arduous. A series of novel sublimable cationic iridium(III) complexes have been designed and synthesized, containing an imidazole‐type ancillary ligand and tetraphenylborate‐type negative counter‐ions with large steric hindrance and well‐dispersed charges. The photophysical properties, electrochemical behaviors, and thermal stability are fully investigated and discussed, then demonstrated by theoretical calculations. Yellow‐ and orange‐emitting OLEDs thereof are fabricated by vacuum evaporation deposition, realizing a high external quantum efficiency of up to 11 %, maximum brightness over 27.3×10 3 cd m −2 and low turn‐on voltages below 2.4 V, among the best results of analogous phosphorescent OLEDs based on iTMCs. This work indicates the promising applications of sublimable iTMCs in state‐of‐the‐art vacuum‐deposited optoelectronic devices.