We investigated the effect of biocompatible silk fibroin (SF):poly(vinyl alcohol) (PVA) blended dielectric layers on the characteristics of N-type organic thin-film transistors (OTFTs). The OTFT with high performance and low driving voltage (4 V) are obtained. Compared with those with pure SF dielectric layer, a high on/off ratio of ∼ 103 and enhanced field-effect mobility of 0.203 cm2/Vs of OTFTs were obtained, by controlling the weight ratio of SF:PVA blends to 7:5. The mechanism of performance improvement of OTFT was systematically studied through the morphology characterization of dielectrics by utilizing atom force microscopy and electrical characterization. The smooth and homogeneous morphology of blend dielectrics having lower charge carrier trap density, is the main reason for the OTFTs based on SF: PVA-blended dielectric exhibited a higher performance than those based on pure SF dielectric.
Organic field-effect transistors (OFETs) using the polymer as the active layer are being intensively developed for flexible electronics including the gas sensor. However, as same as the other kinds of OFET gas sensors, its selectivity is not quite good enough. As we all know, the interfaces, including semiconductor/semiconductor and semiconductor/dielectric, play important roles in gas sensing. In this work, we introduced additional non-conjugated polymer into the polymer active layer, to modulate the selectivity of polymer-based OFET gas sensors to a certain gas. As a result, we can get two kinds of high selective gas sensors based on single polymer OFETs. Both the detection limit, response and selectivity of ammonia and nitrogen dioxide were significantly improved with different non-conjugated polymers, and the device cost was also reduced by a factor of eight as compared to that using pure polymer material. By analyzing the electrical characteristics of OFET sensors and combining with the intrinsic characteristic of the non-conjugated polymers, we systematically studied the mechanism of the performance improvement.
Bottom-gated, top-contact organic field effect transistors (OFET) based nitrogen oxide (NO2) gas sensors were fabricated by incorporating a hybrid organic semiconducting (OSC) layer, which consisting of 6, 13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and Graphene Oxide (GO). By carefully optimizing the proportion of GO in the OSC layer, a tremendous improvement of sensing performance was obtained when exposed to NO2 analyte. Compared with OFET devices based on pure TIPS-pentacene OSC layer, the sensitivity of OFET sensors with hybrid OSC layer had a tenfold enhancement. By analyzing the semiconducting layer through utilizing X-ray diffraction (XPS) and atomic force microscope (AFM), the enhanced sensing performance was attributed to the absorption of the NO2 gas molecules through a porous OSC layer and a preferable interaction between functional groups on the edge of GO sheets and NO2 gas molecules. The improved sensing performance by the hybrid OSC layer also suggests the possibility of GO for the further application in high performance OFET based gas sensors.
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