Spiro-functionalized Ligand with Supramolecular Steric Hindrance to Control pi-pi Interaction in the Iridium Complex for High-Performance Electrophosphorescent Devices

Supramolecular steric hindrance (SSH) originates from the combination of the steric hindrance effect of rigid and bulky three-dimensional (3D) moieties with a weak supramolecular interaction. Orthogonally bulky spirobifluorene as a pi-pi 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), eta(L) of 44.3 cd.A(-1), and eta(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.