Spiro-functionalized ligand with supramolecular steric hindrance to control π-π interaction in the iridium complex for high-performance electrophosphorescent devices

Supramolecular steric hindrance (SSH) originates from the combination of the sterichindrance effect of rigid and bulky three-dimensional (3D) moieties with a weak supramolecular interaction. Orthogonally bulky spirobifluorene as a π-π stacking SSH model was incorporated into a homoleptic Ir complex. Ir(SFP)₃ with SSH exhibits impressive higher quantum yields and spectral stability than that of its alkyl-substituted counterpart Ir(BFP)₃. The lower turn-on voltage and higher optimized dopant concentration for Ir(SFP)₃ were observed in the proof-in-concept phosphorescent organic light-emitting diodes (PHOLEDs) exhibiting a higher maximum brightness (L_max) of 35481 cd·m^-2, η_L of 44.3 cd·A^-1, and η_P of 34.8 lm·W^-1. The probable supramolecular architectures of dopant-dopant and host-guest interactions were proposed on the basis of molecular modeling.