ETP Annual Conference 2017
Edinburgh, 10th October 2017
Indacenodithiophenes as Small-Molecule n-Type Semiconductors for Organic Solar Cells
C. E. A. Gottardi1, A. Pron2, L. Nanson2, G. Morse2, I. D. W. Samuel3 and G. Cooke4
1 School of Chemistry, WestCHEM, University of Glasgow, University Avenue, Glasgow, G12 8QQ, U.K.,
2 Merck Chemicals Ltd., Chilworth Technical Centre, University Parkway, SO16 7QD Southampton, U.K.,
3 School of Physics & Astronomy, Physical Science Building, North Haugh, St Andrews, U.K.,
4 School of Chemistry, WestCHEM, University of Glasgow, University Avenue, Glasgow, G12 8QQ, U.K.,
Abstract
Organic excitonic solar cells are steadily advancing as a promising new technology for harvesting sunlight and have recently achieved power conversion efficiencies of up to 11.5 % for single junction [1] and 13.2 % for multiple-junction [2] devices respectively. A short energy payback time, low or zero toxicity, abundance of elements and device flexibility are their chief advantages, but some challenges including monetary cost remain whilst a further improvement of the efficiency is equally desirable. The most commonly employed electron acceptor materials, which along with the donor material make up a device’s p-n heterojunction, belong to the class of fullerenes and their derivatives, such as C60 and PC60BM. Whilst the latter have advantages such as very good and anisotropic charge transport, the energy of their frontier molecular orbitals can scarcely be tuned, their absorption spectra have poor overlap with the solar spectrum and they are a substantial item in the overall device cost. The search for alternatives is therefore an active field of research. Recent advances in efficiency in fullerene-free organic solar cells based on indacenodithiophene-based small molecule acceptors have been achieved by Xiaowei Zhan and co-workers [3, 4, 5]. This project aims to further optimise the properties of these promising acceptor dyes by modifying various functional groups and side chains. The electronic properties of the dyes can be predicted by Density Functional Theory calculations which guide the choice of synthetic targets.
Figure 1: Generic structure for target molecules
References
[1]J. Zhao, Y. Li, G. Yang, K. Jiang, H. Lin, H. Ade, W. Ma, and H. Yan, "Efficient organic solar cells processed from hydrocarbon solvents", vol. 1, Nature Energy, 2016, article number 15027.
[2]"Heliatek sets new Organic Photovoltaic world record efficiency of 13.2%", Press Release, Heliatek GmbH, Dresden, Germany, 08/02/2016.
[3]Y. Lin, Z.-G. Zhang, H. Bai, J. Wang, Y. Yao, Y. Li, D. Zhu, and X. Zhan, "High-performance fullerene-free polymer solar cells with 6.31% efficiency", vol. 10, Energy & Environmental Science, 2015, pp. 610 - 616.
[4]Y. Lin, J. Wang, Z.-G. Zhang, H. Bai, Y. Li, D. Zhu, and X. Zhan, "An Electron Acceptor Challenging Fullerenes for Efficient Polymer Solar Cells", vol. 27, Advanced Materials, 2015, pp. 1170 - 1174.
[5]Y. Lin, Q. He, F. Zhao, L. Huo, J. Mai, X. Lu, C.-J. Su, T. Li, J. Wang, J. Zhu, Y. Sun, C. Wang, and X. Zhan, "A Facile Planar Fused-Ring Electron Acceptor for As-Cast Polymer Solar Cells with 8.71% Efficiency", vol. 138, Journal of the American Chemical Society, 2016, pp. 2973 - 2976.