Highly Sensitive and Selective Room Temperature-Operated NO2 Sensor Based on Eco-Friendly Water Processed Low Voltage Operable OFET

Abstract

We report a highly sensitive and selective room temperature (RT) operated nitrogen dioxide (NO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}{)}$ </tex-math></inline-formula> Gas Sensor based on Low voltage Operable poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5di(thien-2-yl)thieno [3,2-b]-thiophene)] (DPP-DTT) based organic field effect transistors (OFETs). We have used water-induced aluminum oxide (AlO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{x}{)}$ </tex-math></inline-formula> as gate dielectric and the floating film transfer method (FTM) using water as a liquid substrate to lift the self-assembled film of DPP-DTT. The fabricated OFET devices were operated at a low voltage of −3 V. The device was tested for low-voltage Gas sensing applications. The DPP-DTT OFETs-based Gas sensor showed a response of 2217.4% for 200 ppb and 8445.5% for 1.4 ppm of NO2, respectively at (RT, 25 °C) and relative humidity (RH) of 55%. The respective percentage changes in mobility and threshold voltage were 1210.81 and 121.92 for 1.4 ppm of NO2. The DPP-DTT-based NO2 sensor recorded a response and recovery time of 34 and 168 s for 1.4 ppm NO2. The maximum temperature in the whole fabrication process was not more than 260 °C. A selective study with SO2, NH3, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{{2}}\text{S}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{{2}}$ </tex-math></inline-formula> , and CO2 was also done which establishes the high selectivity of the sensor for NO2. This report combines the benefits of the eco-friendly processing technique for AlOx dielectric, floating film transfer from water substrate instead of commonly used toxic ethylene glycol, and superior gas sensing properties of FTM film.