- Time: 03:00 p.m.-05:00 p.m.
- Date: Mar. 17, 2023
- Venue:SC140 (onsite) and https://core.xjtlu.edu.cn/mod/bigbluebuttonbn/view.php?id=283114 (BBB link)
- Speaker: Prof. John Dennis
- Topic:Fullerene for Solar Cells
The as-produced isomer mixture of the organic photovoltaic device acceptor material bisPCBM has been purified into its constituents by peak-recycling HPLC, and those individual isomers were characterized by UV-Vis absorption spectroscopy and cyclic voltammetry. A total of 19 isomers were purified from the mixture to a standard exceeding 99.5% with respect to other isomers. The HOMOs, LUMOs, and HOMO–LUMO gaps of the purified isomers vary from 5.673 to 5.444 eV, 3.901 to 3.729 eV, and 1.664 to 1.883 eV, respectively Each isolated isomer was structurally identified by 13C NMR spectroscopy coupled with DFT simulations and similarities/difference between the 19 UV-Vis absorption spectra. These results show that every isomer is a methano-fullerene, and as there are only 19 possible methano-fullerene isomers of PCBM, that all such isomers form with roughly similar yields – but with a slight preference for the near-equatorial positions, and somewhat diminishes yields for the near-polar sites. We also find a correlation between HPLC retention time and the relative positions of the addends; in that generally the closer the addends are to each other the longer the retention time of the isomer, and vice versa. In addition photovoltaic devices based on the isolated isomers have been fabricated and studied.
Prof. John Dennis gained his D.Phil. from the University of Sussex in 1993 under the supervision Harry Kroto. After publishing 30 papers in 3 years as a graduate student (including three in Nature), all his postdoctoral Research was conducted under internationally competitive personal research fellowships (from the Australian Research Council, The Japan Society for the Promotion of Science and the Alexander von Humboldt Foundation). He then gained tenure at Queen Mary University of London in the Department of Chemistry in 1999 and transferred to the Physics Department at the same institution with a promotion to a professorial position in 2005.
He joined the department of Chemistry at XJTLU in October 2022. Immediately before this he worked as Professor at Zhejiang University for two years, being brought to China via a 'High-Level Foreign Expert Award' from the Zhejiang Province 1000 Talent Plan in 2020. He has published almost 100 papers on fullerenes that average over 80 citation per paper, generating an h-index of 40.