Near-IR Emitting Iridium(III) Complexes with Heteroaromatic β-Diketonate Ancillary Ligands for Efficient Solution-Processed OLEDs: Structure-Property Correlations

Three NIR‐emitting neutral IrIII complexes [Ir(iqbt)2(dpm)] (1), [Ir(iqbt)2(tta)] (2), and [Ir(iqbt)2(dtdk)] (3) based on the 1‐(benzo[b]thiophen‐2‐yl)‐isoquinolinate (iqtb) were synthesized and characterized (dpm=2,2,6,6‐tetramethyl‐3,5‐heptanedionate; tta=2‐thienoyltrifluoroacetonate; dtdk=1,3‐di(thiophen‐2‐yl)propane‐1,3‐dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR‐emitting, solution‐processed phosphorescent organic light‐emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1) with negligible efficiency roll‐off values, exceeding the highest reported values for solution‐processible NIR emitters. Let's glow: Heteroleptic benzo[b]thiophenyl isoquinolinate IrIII complexes with diketonate ancillary ligands of increasing conjugation were prepared. The compounds are NIR emissive with high emission quantum yields (up to 16 %). A solution‐processed OLED fabricated with one of the complexes demonstrates a remarkable external quantum efficiency (EQE) of more than 3 % with negligible efficiency roll‐off.