Application of wide-energy-gap material 3.4-di(9H–carbazol-9-yl) benzonitrile in organic light-emitting diodes

Publication date: Available online 10 November 2016
Source:Thin Solid Films
Author(s): Yuya Tanaka, Takehiro Takahashi, Junichi Nishide, Yasuhide Hiraga, Hajime Nakanotani, Chihaya Adachi
A material with a wide energy gap, 3.4-di(9H–carbazol-9-yl)benzonitrile (2CzBN), was synthesized and applied in organic light-emitting diodes (OLEDs). Pure blue electroluminescence with a peak wavelength of 436nm and Commission Internationale de l'Èclairage (CIE) coordinate of (0.160, 0.084) were obtained for an OLED containing 2CzBN as an emitter, although its external emission efficiency was limited to around 1% because of the lack of thermally activated delayed fluorescence (TADF) activity. In contrast, a highly efficient TADF-based OLED was obtained when 2CzBN was used as a host instead of an emitter by taking advantage of the high triplet energy (2.92eV) and unexpected electron transport capability of 2CzBN.