Bipolar anthracene derivatives containing hole- and electron-transporting moieties for highly efficient blue electroluminescence devices

A series of bipolar anthracene derivatives containing hole-transporting triphenylamine and electron-transporting benzimidazole moieties were synthesized and characterized. These compounds possess high thermal properties and quantum yield in toluene solution but their photoluminescence spectra are sensitive to the polarity of the solvent. Three types of devices were fabricated to investigate their electron-transporting and hole-transporting as well as light-emitting properties. The electroluminescence spectra for the three derivatives B1, B3 and B4 show that they emit blue light, while the B2-based devices produced white light at a low current density because of the electromer formation. Moreover, a single layer OLED device for B4 exhibited a current efficiency of 3.33 cd A^-1 with a pure blue color of CIE _(x,y) of (0.16, 0.16) at 20 mA cm^-2 and a maximum brightness of 8472 cd m^-2 at 8.7 V.