Design,Construction And Applications Of Organic Field Effect Transistor Gas Sensors

In recent years,the rapid development of Internet of Things,artificial intelligence,wearable electronics and other technologies has put forward a higher demand for sensors.Among them,gas sensors have entered a new stage of miniaturization,intelligence and multi-function.Compared to resistor devices,organic field-effect transistors（OFET）attract much attention in gas sensors because of several fascinating advantages,such as miniaturization,highly integrated,low cost,easy processing,low operating temperature,as well as multi parameters,signal amplification and molecular design capability.Recently,OFET-based gas sensors have made some progress.However,the low sensitivity,slow room-temperature response/recovery speed,poor selectivity,limited function and poor compatibility with flexible electronic skin remain great challenges in developing OFET-based gas sensors.To address the above issues,we select the OFETs as sensing element with the optimized fabrication process and device configuration,and investigated their applications in intelligent sensing.The main results are as follows:1.Several kinds of porous polymer ultrathin film have been constructed by phase inversion for ultra-sensitive NO₂ detection.The pore size and porosity of porous films can be controlled by changing the immersion time and solvent properties.The porous PCDTPT ultrathin film transistor exhibits excellent sensing properties towards NO₂ when solvent is chlorobenzene and immersion time is 3 s.The limit of detection down to sub-ppm level.The sensing response is as high as 2.5×10⁶%towards 30 ppm NO₂,which is more than one order of magnitude higher than the reported highest value.Futher,porous structure also improves the selectivity of PCDTPT towards NO₂ over the dense PCDTPT ultrathin film.The excellent sensing performances benefit from the exposure conductive channel,which provides direct routes for the diffusion of gas molecules and promotes the direct interaction between gas molecules and carriers.This is the first demonstration of porous organic semiconductor film by phase inversion.This efficient and pollution-free method exhibits good universality,opening up a novel stragety in constructing the high-performance organic gas detectors.2.Based on the slow response/recovery properties of organic semiconductors to gas molecules at room temperature,A flexible conformable artificial organ-damage memory system towards hazardous gas leakage is constructed based on a single OFET for the first time.The room-temperature gas sensing properties of PCDTPT OFET in the sustained adsorption and slow desorption endow the bionic device with the gas-controlled memristive effect without introducing external memory elements.This facile electronic device geometry ensures accumulation of the sensing signal towards the single prolonged NO₂ exposure and the long-term repeated NO₂ exposure,allowing the system to simulate the inhalation,metabolism and cumulative organ damage of the human body upon hazardous gas leakage.Such system breaks through the traditional application of OFETs in gas detection,and exhibits the potential for future medical monitoring and non-invasive diagnosis in a portable and wearable sensing platform.3.Based on the multi-parameter characteristics of OFET,the ZnPc single nanobelt field-effect transistor with the gas dielectric was fabricated for high-response identifiable gas sensor.The single ZnPc OFET can response to NO₂,SO₂ and H₂S with a low LOD of 50 ppb at room temperature.The response towards 10 ppm NO₂ and 20 ppm H₂S is as high as 220%and 3566%,respectively.By combining the differentiable multiple field-effect parameters under different gas atmospheres with linear discriminant analysis model,our single ZnPc nanobelt transistor exhibits the strong gas identification capacity among single-component NO₂,SO₂ and H₂S with 92%success ratio.The excellent sensing performance is attributed to the regulation of shallow defects in organic semiconductor by gas molecules,and exposed conductive channel with the enhanced sensitivity.This method provides an effective strategy for the high performance,low power consumption and high integration of bionic olfactory system.