Durable transparent carbon nanotube films for flexible device components

• Published in: Thin solid films Vol. 518; no. 23; pp. 6977 - 6983
• Main Authors: Sierros, K.A., Hecht, D.S., Banerjee, D.A., Morris, N.J., Hu, L., Irvin, G.C., Lee, R.S., Cairns, D.R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.09.2010; Elsevier
• Subjects: Applied sciences; Carbon nanotubes; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Damage; Devices; Durability; Electro-mechanical properties D; Electrodes; Electronics; Exact sciences and technology; Failure; Flexible devices; Indium tin oxide; Materials science; Mathematical models; Mechanical and acoustical properties; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Nanotubes; Optoelectronic devices; Other topics in nanoscale materials and structures; Physical properties of thin films, nonelectronic; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Strain; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Carbon nanotubes; Flexible devices; Electro-mechanical properties D; Solar cells; Scratching test; Indium tin oxide electrode; Cracking; Mechanical properties; Optoelectronic devices; Elastic deformation; Indium oxide; Thin films; Transparent thin film; Poisson ratio; Tin oxide; Electric resistivity; Uniaxial strain; Conductive coating; Damage; Nanostructured materials
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.07.026

This paper describes a durable carbon nanotube (CNT) film for flexible devices and its mechanical properties. Films as thin as 10 nm thick have properties approaching those of existing electrodes based on indium tin oxide (ITO) but with significantly improved mechanical properties. In uniaxial tension, strains as high as 25% are required for permanent damage and at lower strains resistance changes are slight and consistent with elastic deformation of the individual CNTs. A simple model confirms that changes in electrical resistance are described by a Poisson's ratio of 0.22. These films are also durable to cyclic loading, and even at peak strains of 10% no significant damage occurs after 250 cycles. The scratch resistance is also high as measured by nanoscratch, and for a 50 μm tip a load of 140 mN is required to cause initial failure. This is more than 5 times higher than is required to cause cracking in ITO. The robustness of the transparent conductive coating leads to significant improvement in device performance. In touch screen devices fabricated using CNT no failure occurs after a million actuations while for devices based on ITO electrodes 400,000 cycles are needed to cause failure. These durable electrodes hold the key to developing robust, large-area, lightweight, optoelectronic devices such as lighting, displays, electronic-paper, and printable solar cells. Such devices could hold the key to producing inexpensive green energy, providing reliable solid-state lighting, and significantly reducing our dependence on paper.