Abstract
High-response organic field-effect transistor (OFET)-based NO2 sensors were fabricated using the synergistic effect the synergistic effect of zinc oxide/poly(methyl methacrylate) (ZnO/PMMA) hybrid dielectric and CuPc/Pentacene heterojunction. Compared with the OFET sensors without synergistic effect, the fabricated OFET sensors showed a remarkable shift of saturation current, field-effect mobility and threshold voltage when exposed to various concentrations of NO2 analyte. Moreover, after being stored in atmosphere for 30 days, the variation of saturation current increased more than 10 folds at 0.5 ppm NO2. By analyzing the electrical characteristics, and the morphologies of organic semiconductor films of the OFET-based sensors, the performance enhancement was ascribed to the synergistic effect of the dielectric and organic semiconductor. The ZnO nanoparticles on PMMA dielectric surface decreased the grain size of pentacene formed on hybrid dielectric, facilitating the diffusion of CuPc molecules into the grain boundary of pentacene and the approach towards the conducting channel of OFET. Hence, NO2 molecules could interact with CuPc and ZnO nanoparticles at the interface of dielectric and organic semiconductor. Our results provided a promising strategy for the design of high performance OFET-based NO2 sensors in future electronic nose and environment monitoring.
Highlights
Since air pollution has become an urgent global problem with the development of industry and technology, detecting gases, especially toxic gases, as the basis for controlling air pollution, has become increasingly significant [1]
Optical methods, which rely on the unique optical fingerprints of NO2 gas molecules, have the highest sensitivity despite their sizes and costs [7]
NO2 sensing based on resistive relies on the charge transfer between metal oxides and NO2 absorbed on the surface, which has poor selectivity and needs high temperature to achieve recovery or reaction [9]
Summary
Since air pollution has become an urgent global problem with the development of industry and technology, detecting gases, especially toxic gases, as the basis for controlling air pollution, has become increasingly significant [1]. The potential detrimental impact of NO2 emission on public health and the environment has led to extensive scientific and Sensors 2016, 16, 1763; doi:10.3390/s16101763 www.mdpi.com/journal/sensors. Electrochemical sensing mainly depends on electrochemical reduction between NO2 and catalysts, which is low-cost but has a short lifetime [8]. NO2 sensing based on resistive relies on the charge transfer between metal oxides and NO2 absorbed on the surface, which has poor selectivity and needs high temperature to achieve recovery or reaction [9]. With the development of two-dimensional (2D) materials, Ou et al have realized selective and reversible NO2 gas sensing by using the charge transfer between physisorbed NO2 gas molecules and 2D tin disulfide (SnS2 ) and molybdenum disulfide (MoS2 ) at low operating temperatures [10,11]
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