6/9/13 A transparent electrode based on a metal nanotrough network

Paper:

A transparent electrode based on a metal nanotrough network

Hui Wu, Desheng Kong, Zhichao Ruan, Po-Chun Hsu, Shuang Wang, Zongfu Yu, Thomas J. Carney, Liangbing Hu, Shanhui Fan & Yi Cui

Keywords: Transparent conductor, plasmonics, thermal evaporation, nanotube, thinfilm, electrospinning, flexible electronics, nanotrough, transfer film

Dead Body: conventional TCOs are good, but most are not flexible, transparent, and highly conducting at the same time. Furthermore, TCOs can have low infrared transmittance.  CNTs and NW transparent conductors are good, but they aren't usually conducting enough.

Prior work: lots of citations on previous transparent conductors such as ITO, graphene, CNTS, Ag NWs, Ag grid, and Ni film.

Solution: 

Background: electrospun PET can be spun over large lengths, and therefore is good for larger industrial applications. Also, electrospinning achieves a spatially uniform distribution of nanofibers, which helps to achieve a high percolation parameter (aspect important to make sure that current doesn't have to travel through a non-uniform network).

What are the most interesting results: 

• The nanotrough design is sufficiently thin to be mostly transparent, but also doesn't cover as large of an areas as a nanoribbon, so it doesn't block as much light.
• the transmission spectral is flat, meaning that they don't absorb at any particular wavelength from 300-2000nm.  This is possibly because they are below this spectrum cutoff (about 200nm diameter), but also not small enough to show quantum characteristics like NPs.
• They are decently chemically stable
• They are extremely flexible and stretchable.  Bending to a radius of 2mm or 20mm X 2000 bendings didn't reduce the conductivity.  Furthermore, they could be stretched at 50% and still only increase resistance by 40%. Lastly, on paper, they were crumpled up, then shown to still conduct
• They can be transferred with tape.
• 
  

What are the most interesting discussions:

• FE simulation was done to test the TM and TE excitation of light based on the nanotroughs.  It is interesting to note the magnification (up to 8 times) of fields was either at the tips of the troughs, or at the U's of the trough.  As is appropriate, they suggested that this might be useful for applications where the fields need to be magnified inside this conductor. The TE polarization "focuses" the light into the U of the trough, which is pretty neat! 
• Pretty interesting that the nanotroughs are so useful.  it seems that it is simply because they have a smaller x-sectional area that they let more light through than nanowires, and the e-beam deposition means that the metal grains have fewer defects.  otherwise, why is a nanotrough better?

Materials used: 

• PVA nanofibers electrospun
• Au, Ag, Cu, Al thermally evaporated
• transfer substrate: glass, PET, plastic, textile, paper, curved flask

How this applies to my work:

• Do I have anything that needs to be patterned inside of these nanotroughs?  They are interesting, but what could they be used for?
• The electrospinning of nanofibers could be used as a substrate for polymers as well.
• Could this work as a TEM grid? or suspension grid for annealing between the troughs?
• If the diameter of the trough is commensurate with a particular self-assembly system, or synthesis of a nanomaterial, it might help to make higher order structures or materials.

Applications:

Cited - optoelectronic devices, resistive-touch-screen devices, solar cells, solar fuel, photo-assisted chemical reactions, and optical sensors

My own - templated assembly within the nanotroughs, TEM grids, something that requires this transverse electric field along the length of the nanotrough,