LAUSR

Abstract A series of dipolar 1,3,6,8-tetrasubstituted pyrene-based compounds (py1, py2, mpy1 and mpy2) were designed and synthesized with two 4-tert-butylphenyl segments at 1,8-positions and two electron-transporting benzimidazole moieties at 3,6-sites of the pyrene core. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. Moreover, the structure of compound py1 was determined by single-crystal X-ray diffraction analysis, indicating that the compound has a non-coplanar structure and there is no π-π stacking between the molecules. The benzimidazole moieties attached on the pyrene ring via para- and meta-linking modes and by changing the molecular linkage from para-to meta-mode can effectively tune the emission to pure blue region. The four compounds exhibit high absolute fluorescence quantum yields in dichloromethane (99.89–100%) and in film states (54.56–86.78%). In addition, the meta-linked compounds mpy1 and mpy2 exhibit higher absolute fluorescence quantum efficiencies in solution and film states than the para-linked compounds py1 and py2, which demonstrates that the meta-linked architecture can more effectively twist the molecule and suppress the intermolecular interactions. All these compounds exhibit high thermal stability and can form morphologically stable amorphous thin films with glass transition temperature in the range of 182–215 °C. Two types of non-doped blue OLED devices were fabricated using compounds py2 and mpy2 as representatives to investigate their light-emitting and electron-transporting properties and the devices exhibit promising device performance. The devices using meta-linked compound mpy2 as emitting and electron-transporting layers shows pure blue color purity (0.16, 0.10) with high current and power efficiencies (2.70 cd A−1, 1.97 l m W−1).