Innovative Approach to Photo-Chemiresistive Sensing Technology: Surface-Fluorinated SnO2 for VOC Detection

Abstract

Transparent electronics continues to revolutionize the way we perceive futuristic devices to be. In this work, we propose a technologically advanced VOC (volatile organic compound) sensor in the form of a thin film transparent display which is fabricated by using fluorinated SnO2 films. A solution processed method for surface fluorination of SnO2 films using SelectfluorTM as fluorinating agent, has been developed. The doped fluorine was optimised to be < 1% resulting in a significant increase in conductivity and reduction in persistent photoconductivity accompanied by a faster decay of the photogenerated charge carriers. A combination of these modified properties together with the intrinsic sensing ability of SnO2 were exploited in designing a transparent display sensor for ppm level detection of VOCs at an operating temperature of merely 150 °C. Even, a transparent metal mesh heater is integrated with the sensor for the ease of operation, portability and less power usage. A sensor-reset method is devised while shortening the UV exposure time, enabling complete sensor recovery even at lesser operating temperatures. The sensor is tested towards a variety of polar and non-polar VOCs (amines, alcohols, carbonyls, alkanes, halo-alkanes and esters) and it exhibits an easily differentiable response with the sensitivity falling in-line with the electron donating tendency of the functional group present. This work opens up door for multiplexed sensor arrays with ability to detect and analyze multiple VOCs with specificity.