Biphenyl Diimide Based Novel Blue Emitters with Aggregation‐Induced Blue‐Shifted Emission Characteristics

Abstract

AbstractTwo biphenyl diimide (BPI) monomers containing seven‐membered imide rings and four conjugated aromatic diimides, BPI‐Ph, BPI‐Th, BPI‐Se and BPI‐Py, with unique aggregation‐induced blue‐shifted emission (AIBSE) properties, are reported. The crystal structures revealed that the imide backbones were twisted, leading to weaker 1D π‐stacking, which makes the compounds very different from other reported imides. Their cyclic voltammetry, UV/Vis absorption and fluorescence spectra, as well as DFT calculations, were investigated in detail. The photophysical properties and aggregation behaviors of BPI‐Ph, BPI‐Th, BPI‐Se and BPI‐Py in mixtures of THF/water were systematically studied. The intriguing AIBSE of the BPI‐containing compound was attributed to the lower reorganization energies in aggregates than in the solution phase, ascribed to the lack of π‐stacking resulting from the twisted seven‐membered rings, restricted intramolecular rotation (RIR) and weak intermolecular interactions in the solid state. Additionally, BPI‐Py‐based OLEDs exhibited good performance of Lmax, ηC,max, ηP,max and ηext,max up to 6014 cd m−2, 6.41 cd A−1, 5.50 lm W−1 and 3.85 %, respectively. The presented results provide a new strategy to design blue emitters in the future.