Material- and energy-efficient production of ultra-transparent electrodes based on rodlike conductive nanoparticles
Since product life cycles of displays become shorter the electronic industry is seeking for the usage of alternative materials to conventional indium tin oxide (ITO) as a material for transparent electrodes. Several materials such as nanocarbon or silver nanowires have been discussed in literature. However, a commercial replacement of ITO has not set in yet since each of the alternative materials performs weil in a certain property but underperform in another compared to ITO. We will present our recent results on transparent conductive films made of co-percolating silver nanowires and carbon nanotubes. This combination Ieads to superior optoelectrical performance of the ultratransparent electrodes. We will outline the huge potential of electrical co-percolation of rodlike conductors based on theoretical and experimental data. Furthermore we will report on scalable manufacturing processes of these films on commercial smart phone cover glasses and flexible foils for roll-to-roll manufacturing. The liquid film coating technique is analysed with regard to technical suitability and cost efficiency. We were able to produce transparent conductive films with material costs less than three US Dollars per square meter. The ultra-transparent electrodes exhibit optical transmission of 98 % with sheet resistance of 70 Ohm / sq. The optical haze, which is usually a crucial drawback of silver nanowire films, is within the industrial tolerance of today's quality standards. Transparent conductive films are an important research topic. Our contribution will discuss fundamental principles such as electrical percolation theory as weil the industrial feasibility of ITO replacement.