Focus I Carbon Nanotubes


Driving innovation in display technology


One of the most exciting chemical discoveries of recent times, Dr Sian Fogden looks at how carbon nanotubes could offer an entirely new material system


C


arbon nanotubes are one of the most exciting chemical discoveries of recent times, offering an opportunity for an


entirely new material system to be developed. Single walled carbon nanotubes (SWNTs), which are 10,000th the diameter of a human hair, are an allotrope of carbon - like graphite and diamond - and they have unique physical and electronic properties. These properties include a higher axial thermal conductivity than diamond; greater axial mechanical strength than steel (orders of magnitude by weight); and larger current capacity than copper. These unique properties mean that carbon nanotubes are likely to be of great importance in the future of materials.


Dr Sian Fogden 10 October 2013


Current monopoly Transparent conductive thin films (TCFs) are


Components in Electronics


used in most high tech displays and touch screens. Currently the electronics industry relies primarily on one material for these displays – indium tin oxide (ITO). Although its core properties - transparency of greater than 85% and conductivity~5Ω/sq - make ITO the materials leader, it is far from perfect. Its processing cost is high as it uses expensive vacuum techniques and with the current drive for decreased cost it cannot be scaled accordingly. Other properties are much less desirable and in some instances even prohibit device innovation. Take its ceramic nature which makes it brittle and therefore unsuitable for flexible displays and prone to cracking. All of the largest display makers agree an alternative to ITO must be found. This is why there is a gap in the market for single walled carbon nanotubes


(SWNT). Whilst offering


exceptional transparency and conductivity, their mechanical flexibility, durability,


neutral colour, lower reflection, compatibility with solution based deposition processes and inherently lower cost make them an excellent alternative to ITO. Up until this point technical barriers have stopped the unique SWNT properties from being fully exploited. SWNTs are very long (in the order of 10s of microns) and very thin (approximately 1nanometers) so they have a very high attractive force between individual tubes, agglomerating into ropes and bundles. However, before SWNTs can be used to make TCFs they must be physically separated from one another and dissolved into solution.


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