Inkjet-Printed Conductive ITO Patterns for Transparent Security Systems

Indium tin oxide (ITO) is a transparent conducting material that is widely used in devices where high transparency of the electrodes is required, such as flat panel and liquid crystal displays, touch panels, smart windows, and many others. ITO layers are deposited on a large scale by magnetron sputtering and then structured by lithography to define desired patterns of transparent electrodes. Here, a method for direct printing of transparent conductive patterns from ITO nanoparticle ink is communicated. The method combines inkjet printing with fast flash lamp annealing whereby the main novelty is to use an additional layer of a colored organic dye onto printed ITO to increase light absorption. The dye coating is instantly heated together with the underlying ITO layer by a light pulse, leading to an instant rise of the surface temperature, which is translated into improved optoelectronic properties of the ITO layers. Inkjet-printed ITO patterns processed with the dye-assisted flash lamp annealing exhibit a transmittance of up to 88% at 550 nm and resistivity of 3.1x10(-3)omega cm. Transparent touch-sensing trackpad and capacitive touch sensors are demonstrated based on the printed ITO patterns, which can be utilized in transparent security systems and other transparent Internet-of-Things devices.