Northwestern University ‒ Innuvation ‒ Applied Research Day ABSTRACT

Herbicides and Red Car Paint ‒ Transforming Common Organic Industrial Feedstocks

into Materials for Green Solar Cell Technologies

One of the drawbacks to current state of the art solar cells based on silicon metal is the intensive industrial processing needed in order to construct the necessary n-type and p-type semiconducting materials, and the efficiencies of the photovoltaic cells have nearly been optimized to the theoretical limit (1) of 30%. The cost per unit energy is not enough to make this technology dominate the energy market as long as fossil fuels remain relatively inexpensive. Organic-based solar cells, the fabrication of which can be carried out with far less intensive processes, promise a reduction in costs, while maintaining efficiencies and scalability comparable to silcon-based technologies. In order for organic solar cells to be efficiently utilized as the photoactive electronic components of photovoltaic cells, organic materials (2) must absorb light strongly in the solar spectrum and be semiconductive in the solid state. Towards this end, we have researched and investigated the electronic and photonic properties of two commonly available industrial chemicals – methyl viologen and perylene diimide – and their derivatives. Methyl viologen, a popular herbicide known by its trade name “paraquat”, and the inexpensive perylene diimide, the chemical employed as pigment in red car paint, are two widely available chemical compounds. Using methyl viologen and derivatives thereof, we have developed a library of p-type organic semiconducting materials. The science of our patent-pending (3) technology relies on the efficient self-assembly of interchangeable pairs of methyl viologen and its derivatives, which we have demonstrated leads to their strong light-absorbing properties and solid-state semiconducting behavior. The modularity of our approach allows us to mix and match a library of derivatives of the methyl viologen molecule, all with their own unique electronic properties, in order to tune and optimize these materials when constructing solar cell devices. Our research has also investigated the semiconductive and photonic properties of simple derivaties of perylene diimide, and we have shown that this common industrial feedstock can be easily converted between n-type and p-type semiconducting materials through simple, one-step synthetic modifications. We propose to construct a prototype solar cell incorporating these organic semiconductors derived from herbicides and red car paint industrial feedstocks. The fact that many of these materials can be synthesized and processed using water and ethanol mixtures, avoids many toxic waste products, and adheres to the tenets (4) of Green Chemistry. These materials offer a promising avenue for producing organic photovoltaic cells that are cost competitive in the energy market, while satisfying the consumer and the public by having a relatively low environmental impact.

Bottom Line ‒ Cheap, Green-Processable Materials for Organic Solar Cell Technologies

                                                                                                                         1. W. Shockley, H. J. Queisser, “Detailed Balance Limit of Efficiency of p-­‐n Junction Solar Cells” J. Appl. Phys. 1961, 32, 510. 2. L. Ouahab, E. Yagubskii, Organic Conductors, Superconductors and Magnets: From Synthesis to Molecular Electronics. Kluwer

Academic Publishers, MA, USA (2004). 3. J. F. Stoddart, A. C. Fahrenbach, J. C. Barnes, H. Li, S. Sampath, A. Basuray, U.S. Provisional Patent Application 61/537,852.

“Crystalline Bipyridinium Radical Complexes and Uses Thereof” Filed: September 22, 2011. 4. P. Anastas, N. Eghbali, “Green Chemistry: Principles and Practice” Chem. Soc. Rev. 2010, 39, 301‒312.  

 

 

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