Letter abstract


Nature Materials 8, 208 - 212 (2009)
Published online: 8 February 2009 | doi:10.1038/nmat2379

Subject Categories: Optical, photonic and optoelectronic materials | Materials for energy

Endohedral fullerenes for organic photovoltaic devices

Russel B. Ross1, Claudia M. Cardona2, Dirk M. Guldi3, Shankara Gayathri Sankaranarayanan3, Matthew O. Reese4, Nikos Kopidakis4, Jeff Peet5, Bright Walker6, Guillermo C. Bazan5, Edward Van Keuren1, Brian C. Holloway2 & Martin Drees2

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So far, one of the fundamental limitations of organic photovoltaic (OPV) device power conversion efficiencies (PCEs) has been the low voltage output caused by a molecular orbital mismatch between the donor polymer and acceptor molecules. Here, we present a means of addressing the low voltage output by introducing novel trimetallic nitride endohedral fullerenes (TNEFs) as acceptor materials for use in photovoltaic devices. TNEFs were discovered in 1999 by Stevenson et al.1; for the first time derivatives of the TNEF acceptor, Lu3N@C80, are synthesized and integrated into OPV devices. The reduced energy offset of the molecular orbitals of Lu3N@C80 to the donor, poly(3-hexyl)thiophene (P3HT), reduces energy losses in the charge transfer process and increases the open circuit voltage (Voc) to 260 mV above reference devices made with [6,6]-phenyl-C61-butyric methyl ester (C60-PCBM) acceptor. PCEs >4% have been observed using P3HT as the donor material. This work clears a path towards higher PCEs in OPV devices by demonstrating that high-yield charge separation can occur with OPV systems that have a reduced donor/acceptor lowest unoccupied molecular orbital energy offset.

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  1. Georgetown University, 37th and O st. NW, Washington, District of Columbia 20057, USA
  2. Luna Innovations Incorporated, 521 Bridge Street, Danville, Virginia 24541, USA
  3. Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander- Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
  4. National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, Colorado 80401, USA
  5. Center for Polymer and Organic Solids, University of California, Santa Barbara, California 93106, USA
  6. Department of Chemistry and Biochemistry (or Center for Polymers and Organic Solids) University of California at Santa Barbara, Santa Barbara, California 93117, USA

Correspondence to: Martin Drees2 e-mail: dreesm@lunainnovations.com



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