# Example: Comparison of transparent conductive materials.

This is going to be a short article, based on this table I’ve created: Comparison of transparent electrodes.
This presents a way of comparing materials by their properties directly, using their embodied energy to calculate their cost.  The data is from the LCA study, “Environmental and Economic Assessment of ITO-free Electrodes for Organic Solar Cells” [link, paywalled]

The results are both satisfying and interesting.  Not only are there viable alternatives to Indium-Tin Oxide (ITO), a very popular and very scarce transparent conductor, two of them are actually more cost-efficient, as well.  Surprisingly, a polymer that I have never heard of, high-conductivity PEDOT:PSS (poly(3,4-ethylene dioxythiophene):poly(styrenesulphonic acid)), has similar real-life performance [paywalled] to ITO, while the embodied energy cost is an order of magnitude lower.  The only drawback to this material is that it’s a petrochemical.  Upon discovering this, I began looking for manufacturing techniques for petrochemicals that were not based on petroleum.  I have found Phys.Org articles about chemical engineers producing Xylene from biomass, another about biomass being used to produce five of the six key materials for petrochemicals, and a study [paywalled] about biomass being poised to take over petroleum as the primary feedstock for future petrochemicals.

It only makes sense that a chemical derived from ancient organic matter should be able to be derived from new biomass, with additional steps.  While there doesn’t seem to be an existing process to make PEDOT:PSS from biomass, it seems there may be a bright future for this relatively unknown material.

One other detail that I’ve learned in this example is a general method for comparing materials by their properties: Unit property per megajoule of energy (Which I’ll call UPME until I come up with something better), which is generally calculated like so:$UPME=r_{ro} / r_\varepsilon$
In this example, I used $\frac{S}{cm^2} / \frac{MJ}{cm^2}$, which resulted in the measurement $\frac{S}{MJ}$.  This is a very simple and unambiguous way to compare material properties while also accounting for their costs.

If you need any information from the paywalled articles, contact me.

Update 10/10/14: Since publishing this article, I have been told by people who have better information that PEDOT:PSS has a degradation issue.  By performing the embodied energy analysis over the expected lifetime of the panels, we can account for the potential degradation and replacement cost.