Linearly polarized electroluminescence device in which the polarized plane can be rotated electrically using a chiral liquid crystalline semiconductor
In the electroluminescence from chiral liquid crystals comprising a bis(fluorophenyl)terthiophene unit with macroscopic polarization, two characteristic phenomena were observed. Firstly, linearly polarized light was emitted from the polarized liquid crystal phase under DC bias application, and the polarized plane of the electroluminescence was rotated by 90° owing to the inversion of the polarity of the DC bias applied during the phase transition from the chiral smectic A phase to the chiral smectic G phase. This resulted in a low threshold voltage in 2-μm thick samples having a symmetric structure. Secondly, the hole and electron injection barriers at the electrodes were significantly reduced by the internal electric field produced by the macroscopic polarization of the liquid crystal. This is the first report on linearly polarized electroluminescence with a polarized plane that can be rotated.