Efficient optical terahertz-transmission modulation in solution-processable organic semiconductor thin films on silicon substrate

Terahertz (THz)-transmission modulation through the Si substrate coated with four p-conjugated materials under various laser light irradiation conditions was investigated using THz time-domain spectroscopy. Two of the p-conjugated low molecules, the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), and two of the p-conjugated polymer materials, poly[5-(2-ethylhexyloxy)-2-methoxycyanoterephthalyliden] (MEH-CN-PPV) and poly(benzimidazobenzophenanthroline) (BBL), were investigated. Among these materials, PCBM and TIPS-pentacene showed higher modulation efficiencies and it was also shown that thermal annealing is quite effective in obtaining THz modulation efficiencies higher than those previously reported for copper phthalocyanine. Utilizing these solution-processable p-conjugated materials, various types of THz materials and devices could be fabricated by printing technologies. Our findings may open the way to fabricating various types of THz active devices. (C) 2016 The Japan Society of Applied Physics