[15a-416-1~10] 12.3 Functional Materials and Novel Devices

[15a-416-2] Charge carrier mobility of the bicontinuous cubic liquid crystal having a thiophene backbone by the time-of-flight method

〇Junichi Kougo^1,2, Masanori Yokoyama², Christian Dressel³, Ken Ishikawa², Carsten Tschierske³, Fumito Araoka¹ (1.RIKEN CEMS, 2.Tokyo Tech, 3.MLU)

Keywords:liquid crystal, charge carrier mobility, bicontinuous cubic phase

Lately a bicontinuous cubic phase (Cub_bi) has been attracting an attention as the electronic materials. The resistance to the obstacles to the current in the Cub_bi phase i.e., the defects and the impurities is higher than ones in columnar and smectic phases which are lower dimension transport. Because the Cub_bi phase forms three-dimensional structure which acts as the transport paths for the charge carriers. However, the charge carrier transport in that phase has never reported, except for an ionic transport. To elucidate the electrical properties of the Cub_bi phase are important intrinsically for understanding relationship between a structure and electric property. Therefore, we investigated it to evaluate the charge carrier mobility of the Cub_bi liquid crystal by the time of flight method. The thickness of the sample cells were ca. 5 mm. The third harmonic generation of Nd:YAG pulse laser was used by TOF method as the excited light . The photocurrent was detected by an oscilloscope. The mobility was assessed from the applied voltage, the sample thickness and the transit time which was obtained from the inflection point of the detected photocurrent signals. As the results, we could obtain the mobilities of the positive charged carriers in the Cub_bi and the isotropic phases. While that of the negative charged carriers were detected in only the isotropic phase as ideal current signal shapes. And all regimes of the charge carrier mobilities have thermal activation tendencies. This results suggests that charge carriers in Cub_bi step forward by hopping mechanism.