Carbon nanotubes and graphene for electronics applications 2011-2021
30 September 2011
Transparent electronics is now very much a subject in its own right, and carbon nanotubes (CNTs) and graphene have a huge role to play in this.
CNTs (whether transparent or opaque), graphene and their compounds exhibit extraordinary electrical properties for organic materials, and have a huge potential in electrical and electronic applications such as photovoltaics, sensors, semiconductor devices, displays, conductors, smart textiles, energy conversion devices (such as fuel cells, harvesters and batteries).
A recently released updated report from IDTechEx brings all of this together, covering the latest work from over 110 organisations around the world and details the latest progress in the technologies. New developments, challenges and opportunities regarding material production and applications are given.
Carbon Nanotubes for electronics applications
While the fabrication of CNT transistors is still in the research phases, they are starting to be used for their conductive properties, in addition to the fact that they can be transparent, flexible and even stretchable. In particular, they are being applied as conductive layers for the rapidly growing touch screen market. They are also likely to become a viable replacement for Indium Tin Oxide (ITO) transparent conductors, which are expensive due to the rare Indium being used, vacuum based processing, and additionally have very limited flexing capability, such as easily cracking under 2% strain.
Ink or solution CNTs will enable high performing devices that can ultimately be made in low cost manufacturing processes such as printing, over large areas. Depending on their chemical structure, CNTs can be used as an alternative to organic or inorganic semiconductors as well as conductors, which in electronics, other than electromagnetic shielding, will be one of the first large applications for CNTs. Companies that IDTechEx surveyed forecast growth rates as high as 300% over the next five years.
While the cost of CNTs was once prohibitive, it has been dropping in recent years as chemical companies build up their manufacturing capacity. However, challenges remain and cheap mass production as well as high-volume commercial applications are not yet achieved. The challenges include consistent growth, material purity, separation, device fabrication and the need for other device materials such as suitable dielectrics. Nevertheless, scientists are getting closer - several separation methods have been discovered over the previous few years and a new CNT production process was patented in 2010 by CNano Technology. This, and other new developments regarding the production of pure CNTs and the separation of conducting and semiconducting CNTs are given in this report.
Graphene for electronics applications
Transistors using graphene are considered to be potential successors for the silicon components currently in use. The material proves to be an ideal candidate for many high-speed computing applications in the multibillion-dollar semiconductor device industry; potentially enabling terahertz computing, at processor speeds 100 to 1000 times faster than silicon. Graphene and its compounds are increasingly used to make transistors that show extremely good performance; progress that comes with new cheaper production processes for the raw material.
One crucial issue concerning the use of graphene for electronic applications is getting it to perform as a true semiconductor. However, recent activities of several academic institutions show promise that the material's restraining issue of not having a band gap will soon be solved.
Printable CNT inks and graphene-based inks are beginning to hit the market. The last year has shown further development regarding production, purification and solution processing on both sides.
IDTechEx has researched 113 companies and academic institutions working on CNTs, graphene and their compounds, all profiled in the report. Graphene and multi wall CNTs (MWCNTs) are already in fairly high production. However, most of these uses are for non-electronic/electrical products, or simple applications such as electromagnetic shielding. While manufacturers in North America focus more on single wall CNTs (SWCNTs); Asia and Europe, with Japan in first place and China second, are leading the production of MWCNTs with Showa Denko, Mitsui and Hodogaya Chemical being among the largest suppliers.
Currently, the largest manufacturer in the world is a Chinese company named Cnano, which is reported to produce around 500 tonnes per year. Europe's Bayer Corporation is the second largest global producer at 200 tonnes per year but there are other similar sized producers in Germany and France. However, the largest number of manufacturers, around 27 and albeit at small volumes, is in the United States.
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