Manipulating Excited States of Non-Doped Deep Blue Emitter by Adjusting the Intramolecular Torsion Angle

Abstract

Hybridized local and charge-transfer (HLCT) state of emitters concomitantly featured with high exciton utilization characteristics. However, it remains challenging to simultaneously regulating the excited states and intermolecular packing of blue emitters toward non-doped organic light-emitting diodes (OLEDs) applications. Based on the previously developed star blue emitter TPA-1PN by us, herein we designed and synthesized an isomeric star-shaped blue emitters, namely TPA-4PN, through adjusting the dihedral torsion angles between triphenylamine and phenanthrene fragments. The smaller torsion angle (37.72o) of TPA-4PN than TPA-1PN (61.69o) endows stronger localized excited state characteristics and closer intermolecular packing, leading to higher luminous efficiency associated with a narrower emission spectrum. The corresponding external quantum efficiency of non-doped blue OLEDs based on TPA-4PN reaches 7.76%, with the CIE coordinates of (0.157, 0.071).