Inkjet-Printed Co-continuous Mesoporous Oxides for Surface Dominated Functional Devices

Abstract

Over the last few decades, printed and flexible electronics have emerged as a major area of research, which may cater multiple domains of application requirements for the forthcoming industrial revolution. The solution processed/printed devices can be ideally suited for cost-effective, volume production of sensors and other electronic components that can be connected through Internet of Things (IoT). In this regard, a large variety of sensors may find their application in essential parameter monitoring at industrial premises, wearables, smart textiles, smart appliances, smart packaging, etc., On the other hand, the ability to print the backplane electronics may truly revolutionize the pharmaceutical, diagnostics, and display industries. Next, among available and printable semiconductor technologies (such as polymer, oxides, carbon nanostructures, and various 2D semiconductors) inexpensive, non-toxic, easy-to-print, environmentally stable, abundant, and high mobility metal oxides are believed to have an overall edge in technology commercialization and therefore have been chosen as the printable semiconductor material in the present study. On the other hand, it may be noted that the electronic devices that come under the purview of printed electronics are predominantly surface-dominated devices. Therefore, in this thesis, a soft templating technique has been developed to provide co-continuous, mesoporous structures; the method has earlier been known for fabrication of films using processes, such as dip coating, here, it has now been modified to suit commercial inkjet printing process. A large variety of n- and p-type, undoped and doped, oxide semiconductors (In2O3, SnO2, CuO, Sn: In2O3 (ITO)) have been fabricated with different polymer templating agents to realize printed, large-area, homogeneous, co-continuous, mesoporous structures with large surface-to-volume ratio and pore size varying between 15-50 nm for different semiconducting oxide systems and curing temperatures. The printed mesoporous oxides are then utilized to fabricate fully-printed and extremely high performance (in terms of sensitivity, selectivity, and stability) volatile organic species (e.g. ethanol) sensors or gas (e.g. chlorine, NO2, etc.) sensors. At the same time, identical material systems have been used to fabricate high power printed transistors and fully printed complementary metal-oxide semiconductor (CMOS) electronics on different substrates