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Fullerene Applications

Go to:  Organic Photovoltaics  Polymer Electronics   Antioxidants & Biopharmaceuticals   Additives & Other

Organic Photovoltaics (OPV)

Source: Janssen, et al, MRS Bulletin 1/2005

Pictured here is a schematic of a single layer Organic Solar Cell. The fullerene acts as the n-type semiconductor (electron acceptor). The n-type is used in conjunction with a p-type polymer (electron donor), typically a polythiophene. They are blended and cast as the active layer to create what is known as a bulk heterojunction. Fullerenes are used as is, or they are derivitized to increase their solubility and modify their electronic properties. As the preferred n-type material, fullerenes can comprise up to 75% of the active layer by weight. The most commonly used derivative in photovoltaics is C60, but C70 has been shown to have a 25% higher power conversion efficiency than C60 (Kroon et al, 6/2005). In addition, alternative derivatives such as C60 PCBB have been shown to increase conversion efficiency by over 40% when compared to C60 PCBM in like systems (Zheng, et al, 5/2004).

In August of 2007, Plextronics, Inc. announced that it had set a new efficiency record of 5.4 percent for a single layer OPV cell as certified by the National Renewable Energy Laboratory (NREL), in Golden, Colorado. In June 2008 it also announced that it had begun to market a complete ink system for a 5% efficient OPV cell, and a new certified world record of 5.94%. In January 2009, it announced the opening of a pilot-line for OPV device manufacture. Konarka Technologies which held the prior record of 5.2% (also NREL certified), announced in May of 2009 that it had achieved a certified efficiency of 6.4%. Konarka has likewise made considerable progress toward commercialization. Perhaps their most significant announcement came with their start-up of a 1 Gigawatt OPV device plant in late 2008. The aforementioned efficiency results parallel those published by the Yang group from the University of California Los Angeles which reached similar efficiencies. The UCLA technology has been licensed to Solarmer Energy, Inc., which announced in July 2009 that it had reached a new efficiency record of 6.77%. By November 2009, Solarmer’s devices had reached 7.9%. And finally, in Q’4 2009, Solar-Press, a new entrant in OPV began operations in the UK.

OPV efficiencies are steadily marching upward. With the high levels of commercial and academic research, we will continue to see gains in efficiency. In 2009, Dennler et al (see Dennler, G.; et al; Advanced Materials 2009, 21, 1-16) suggested that practical efficiencies approaching 20% could be achieved using a polymer/fullerene bulk heterojunction device. Combined with roll-to-roll fabrication, grid-competitive solar power is within reach.

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Polymer Electronics

The performance of polymer transistors (Organic Field Effect Transistors (OFETS)) and photodetectors has also been increasing, in part due to a great deal of synergy between OFETS and OPVs. The leading OFETS use the n-type semiconducting properties of fullerenes based on C₆₀, C₇₀ along with C₈₄. Fullerene OFETS fabricated with C₈₄ show greater mobility than C₆₀ or C₇₀ and exhibit greater stability. While more work is needed, the world of polymer electronics is opening up for both fullerenes and single-walled carbon nanotubes.

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Antioxidants & Biopharmaceuticals

Fullerenes are powerful antioxidants, reacting readily and at a high rate with free radicals, which are often the cause of cell damage or death. Fullerenes hold great promise in health and personal care applications where prevention of oxidative cell damage or death is desirable, as well as in non-physiological applications where oxidation and radical processes are destructive (food spoilage, plastics deterioration, metal corrosion).

Major pharmaceutical companies are exploring the use of fullerenes in controlling the neurological damage of such diseases as Alzheimer's disease and Lou Gehrig's disease (ALS), which are a result of radical damage. Drugs for atherosclerosis, photodynamic therapy, and anti-viral agents are also in development.

Fullerenes are known to behave like a "radical sponge," as they can sponge-up and neutralize 20 or more free radicals per fullerene molecule. They have shown performance 100 times more effective than current leading antioxidants such as Vitamin E. Zelens Dermatological Research, launched a skin care cream based on the C₆₀ fullerene. This builds on the earlier launch of Vitamin C₆₀ in Japan.

Nano-C has also conducted a limited series of screening tests for toxicity with a fullerene derivative formulated for lipid solubility. These preliminary tests for ocular tissue toxicity indicate no adverse effects. The picture to the left shows the high level of solubility in almond oil.

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Additives & Other

Polymer Additives

Fullerenes and fullerenic black are chemically reactive and can be added to polymer structures to create new copolymers with specific physical and mechanical properties. They can also be added to make composites. Much work has been done on the use of fullerenes as polymer additives to modify physical properties and performance characteristics.

Other

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