Letter abstract
Nature Materials 5, 197 - 203 (2006)
doi:10.1038/nmat1574
Subject Categories: Polymers | Optical, photonic and optoelectronic materials | Materials for energy
A strong regioregularity effect in self-organizing conjugated polymer films and high-efficiency polythiophene:fullerene solar cells
Youngkyoo Kim1, Steffan Cook2, Sachetan M. Tuladhar1, Stelios A. Choulis1, Jenny Nelson1, James R. Durrant2, Donal D. C. Bradley1, Mark Giles3, Iain McCulloch3, Chang-Sik Ha4 and Moonhor Ree5
Low-cost photovoltaic energy conversion using conjugated molecular materials has become increasingly feasible through the development of organic 'bulk heterojunction (BHJ)' structures1, 2, 3, 4, 5, 6, 7, where efficient light-induced charge separation is enabled by a large-area donor–acceptor interface2, 3. The highest efficiencies have been achieved using blends of poly(3-hexylthiophene) (P3HT) and a fullerene derivative8, 9, 10, 11, 12, but performance depends critically on the material properties and processing conditions. This variability is believed to be influenced by the self-organizing properties of P3HT, which means that both optical13, 14 and electronic15, 16 properties are sensitive to the molecular packing. However, the relationship between molecular nanostructure, optoelectronic properties of the blend material and device performance has not yet been demonstrated. Here we focus on the influence of polymer regioregularity (RR) on the molecular nanostructure, and hence on the resulting material properties and device performance. We find a strong influence of RR on solar-cell performance, which can be attributed to enhanced optical absorption and transport resulting from the organization of P3HT chains and domains. Further optimization of devices using the highest RR material resulted in a power conversion efficiency of 4.4%, even without optimization of electrodes7.
- Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2BW, UK
- Department of Chemistry, Imperial College London, London SW7 2AZ, UK
- Merck Chemicals, Chilworth Science Park, Southampton SO16 7QD, UK
- Department of Polymer Science and Engineering, Pusan National University, Pusan 609-735, South Korea
- Department of Chemistry & Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790-784, South Korea
Correspondence to: Youngkyoo Kim1 e-mail: y.kim@ic.ac.uk
Correspondence to: Jenny Nelson1 e-mail: jenny.nelson@imperial.ac.uk
Correspondence to: Donal D. C. Bradley1 e-mail: d.bradley@imperial.ac.uk
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