Solution‐Processing Electrophosphorescence with High‐Efficiency and Low‐Efficiency Roll‐Off from Iridium(III) Complex Containing Multiple Resonance Core

Abstract Solution‐processing phosphorescent organic light‐emitting diodes (s‐PhOLEDs) based on heavy metal complexes deliver simpler fabrication processes, lower production costs, and higher material utilization rates than thermal‐evaporation phosphorescent OLEDs (t‐PhOLEDs), making them a strong competitor in large‐sized panel manufacturing. However, s‐PhOLEDs face two significant challenges: low electroluminescence efficiency and large efficiency roll‐off at high luminance. Herein, the design and synthesis of an orbitally symmetric octahedral metallophosphor iridium(III) complex (BNPPy)₂‐Ir‐acac containing dual B,N‐embedded multiple resonance emitters are reported. By blending emitter (BNPPy)₂‐Ir‐acac in a p‐n type premixed host, the doped film fabricated by spin coating has a photoluminescence quantum yield of 91% and a horizontal emitting dipole orientation ratio of 73%. The emitter (BNPPy)₂‐Ir‐acac‐based s‐PhOLED exhibits yellow emission with a peak of 552 nm. The external quantum efficiencies (EQEs) are 27.8% and 32.9% at 100 and 1000 cd m⁻², respectively; the EQE reaches a maximum of 33.2% at 2118 cd m⁻²; and the EQEs remain 28.5% and 24.9% at 5000 and 10 000 cd m⁻², respectively.