Project title : Self - sorting of Metallic Carbon Nanotubes for High Performance

SWNTs have superb electronic and mechanical properties; however, SWNTs come in different chiralities making them either metallic (MET) or semiconducting (SC). It is desirable to have only MET tubes in transparent electrode applications. We have recently developed a method to selectively separate the SC and MET SWNTs and form self sorted networks of each on different functionalized surfaces. To enable MET-SWNT networks on other substrates like flexible polymers and quartz, and to increase the density of sorted networks past the surface sorting threshold, we developed a transfer printing method. SWNTs were picked up with nearly 100% yield and transferred intact onto both hydrophobic and hydrophilic surfaces including polymeric and quartz substrates as determined by AFM and UV-Vis spectroscopy. A multi-layer stack was also accomplished using this same method with different surface treated substrates. We plan to use this transfer method to prepare high density MET-SWNT networks for transparent electrode application. We investigated a new method to control the uniformity of carbon nanotube network thin film and its morphology. While carbon nanotube network electrodes show promise, characteristically poor dispersion properties have limited their practicality. We report that addition of small amounts of conjugated polymer to nanotube dispersions enables straightforward fabrication of uniform network electrodes by spin-coating, and simultaneous tuning of parameters such as bundle size and density. After treatment in thionyl chloride, electrodes with sheet resistances as low as 70 ohm/sq with 81% transmittance at 550 nm are obtained; these are among the best reported carbon nanotube based transparent electrodes to date.