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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) like polythiophene. They are blended and cast as the active layer to create what is known as a bulk heterojunction. Fullerenes are used on their own or derivitized to increase their solubility and modify their electronic properties. The most commonly used fullerene derivative in OPV applications is PCBM. 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). The potential for increasing device efficiency through novel fullerene chemistries continues to expand. For example, alternative derivatives such as C60 ICBA have been shown to increase conversion efficiency by over 40% when compared to C60 PCBM in like systems (He, et al., 10/2009, and earlier work by Laird et al (USPTO Application #20100132782)).

Device performance continues to increase, and the field continues to attract investment from large and small companies alike. Where cell efficiencies were 5% in 2005, they have since increased to 8.5% in late 2010. Having set numerous device records from 2007 to 2009, Plextronics, Inc. announced in January 2009 the opening of a pilot-line for OPV device manufacture. It also is marketing a complete ink system for a 5% efficient OPV device. Solarmer Energy, Inc., currently in pilot-scale production, announced in July 2009 that it had achieved a new efficiency record of 6.77%, reached 7.9% by November 2009, and crossed the psychologically important efficiency level of 8% in July 2010. Meanwhile, Konarka Technologies, which held the prior record of 5.2% through 2005, announced in November of 2010 that it had achieved a certified efficiency of 8.4%. 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. Two other start-ups have entered the OPV field. In Q? 2009, Solar-Press, began operations in the UK, and in Q? of 2010, =Eight19, also of the UK, joined the field. Many of these businesses have strategic partnerships in place; Konarka with Total and Minolta, Plextronics with Solvay, and Eight-19 with Rhodia. And in addition, larger companies are investing in this field on their own as well as in joint projects; among them are Mitsubishi Chemical, BASF, /content/language2/html/4942.htm" target="_blank">Bosch, and Merck.

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 organic solar power is within reach.

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 iddtubes.

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.

IDD 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.

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