Dipolar 1,3,6,8-tetrasubstituted pyrene-based emitters containing hole- and electron-transporting moieties: Syntheses, structures, optical properties, electrochemistry and electroluminescence

Abstract

A series of dipolar 1,3,6,8-tetrasubstituted pyrene-based compounds (PyTPA, PyCaZ and Py3CaZ) with a D-π-A configuration were designed and synthesized. The characteristic of these report compounds is that the pyrene core possesses two electron-transporting benzimidazole moieties at 1,8-positions and two hole-transporting arylamine segments at 3,6-sites. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. The intermolecular π-π interactions successfully suppressed in these polysubstituted pyrenes, which leads to relatively high absolute fluorescence quantum efficiencies in film state (73.89–85.74 %). These three compounds exhibit high thermal stability with their decomposition temperature up to 520 °C. Two types of solution-processing devices were fabricated using compounds PyTPA and Py3CaZ as representatives to investigate their electron-transporting, hole-transporting and light-emitting properties. The single layer device based on PyTPA exhibits a current efficiency of 8.02 cd/A and a maximum brightness of 24439 cd/m2 at 7.8 V.