Highly Efficient Orange‐Red‐Emitting OLEDs From Novel BenzothienopyridazineBased Ir (III) Complexes

ABSTRACT Five Ir (III) complexes were successfully synthesized with thieno[2,3‐ d ]pyridazine or benzo[4,5]thieno[2,3‐ d ]pyridazine derivative ligands. Through precise control of the molecular structure of the complexes, specifically, introducing positional isomerism of trifluoromethyl substituents and expanding the conjugated system by introducing tert ‐butylphenyl groups, combined with the synergistic effects of auxiliary ligands, we successfully achieved fine‐tuned regulation of their emission wavelengths from 576 to 612 nm while maintaining high luminescence quantum efficiency (> 88%). The organic light‐emitting diodes (OLEDs) using these materials all achieved maximum external quantum efficiencies (EQE max ) of over 22%. The device based on complex (bptp) 2 Ir(acac) exhibited the best overall performance; its emission wavelength is 612 nm with EQE max of 24.6% and the peak luminance of 148,100 cd/m 2 . These findings not only demonstrate the potential of thienopyridazine/benzothienopyridazine derivatives in developing high‐performance electroluminescent complexes but also establish an effective strategy for wavelength control of Ir (III) complexes.