All solution processed flexible ammonia gas and light sensors based on α,ω-hexyl-distyrylbithiophene films

The aim of this study is to realize flexible photo- and gas sensors using low cost solution processing such as drop casting or ink jet printing. Two organic semiconductors, namely distyrylbithiophene (DS2T) and α,ω-hexyl-distyrylbithiophene (DH-DS2T), were used as active sensor materials. Both oligomers are p-type semiconductors with high mobility and good air stability. While DS2T has a poor solubility in common organic solvent and thus thin films could only processed by thermal evaporation, the highly soluble DH-DS2T allowed the fabrication of all solution processed photo- and gas sensors. The sensor responses were studied by measuring the current through the semiconductor organic film as a function of light intensity (from 2 mW/cm2 to 100 mW/cm2) and ammonia gas concentration (NH3: 25, 50, and 100 ppm) for light and gas sensors, respectively. We demonstrate here that both compounds have efficient sensor responses, Especially the use of DH-DS2T leads to an efficient fully solution processed multifunctional sensor on flexible substrate.