The effect of MWCNTs on the performance of α-sexithiophene OTFT device and its gas-sensing property

In this paper,bottom contact organic thin-film transistor（OTFT）gas sensors were prepared.Silicon dioxide（SiO2）and titanium/aurum（Ti/Au）were used as the insulating layer and the electrode for the device,respectively.The multi-walled carbon nanotubes（MWCNTs）/α-sexithiophene（α-6T）bilayer films were used as the active layer,andα-6T single layer sensitive film was also prepared for comparison purpose.The electrical and trace NO2-sening properties of these two OTFT gas sensors were tested and analyzed.The results showed that,the OTFT device based on MWCNTs/α-6T bilayer had obviously better electrical properties,better stabilities and higher NO2-sening response values than the device withα-6T single layer,in which both the carrier mobility（μ）and on/off current ratio enhanced two order of magnitude.The improved performance of bilayer OTFT can be explained that MWCNTs acted as highly conducting bridges connecting the crystalline terraces in theα-6T film.Threshold voltage（VT）,carrier mobility,on/off current ratio and grid current which showed extremely similar variation trend as source-drain current,were optional parameters to reveal the gas-sensing characteristic of OTFT gas sensors.Morphology analysis showed that the special feature of MWCNTs had certain influence on the gas-sensing properties.