Two novel indolo[3,2-b]carbazole derivatives containing dimesitylboron moieties: synthesis, photoluminescent and electroluminescent properties†
Two novel indolo[3,2-b]carbazole derivatives, 5,11-di(4′-dimesitylboronphenyl)indolo[3,2-b]carbazole (DDBICZ) and 2,8-dimesitylboron-5,11-di(4′-dimesitylboronphenyl)indolo[3,2-b]carbazole (DDDBICZ), were synthesized by introducing two dimesitylboron groups and/or four dimesitylboron groups (as electron-acceptors) into the indolo[3,2-b]carbazole moiety (as an electron-donor). The structures of these two compounds were fully characterized by elemental analysis, mass spectrometry and proton nuclear magnetic resonance spectroscopy methods. Their thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. Their electrochemical and photophysical properties were studied by electrochemical methods, UV-vis absorption spectroscopy and fluorescence spectroscopy. The charge-transporting properties of DDBICZ and DDDBICZ were studied by fabricating single carrier devices using them as charge-transporting layers. The results reveal that DDBICZ and DDDBICZ have high thermal stability (the decomposition temperature of DDBICZ = 201 °C and the decomposition temperature of DDDBICZ = 210 °C) and good electrochemical and electron-transporting properties. Moreover, in order to examine the electroluminescent properties of DDBICZ and DDDBICZ, Device A and Device B were fabricated by using them as light-emitting layers, respectively. The turn-on voltage, maximum luminance and maximum luminance efficiency of Device A are 6.1 V, 5634 cd m−2 and 2.96 cd A−1, whereas those of Device B are 3.6 V, 1363 cd m−2 and 2.88 cd A−1.