Organic photovoltaics and energy: general discussion Justin Hodgkiss, Gary Conboy, Graham Hutchings, Simon Higgins, Ian Galbraith, Neil Findlay, Rupert Taylor, Marc Salle, Shuyu Zhang, Gitti Frey, Ioan B ˆ aldea, Ifor Samuel, Bernd Ebenhoch, Fred Wudl, Ayse Turak, Bingqian Xu, Enrico Angioni, Ravindra Venkatramani, Uli Lemmer, Dmitrii Perepichka, Alexander Kanibolotsky, Peter Skabara, Jack Wildman, Eli Zysman-Colman, Donal Bradley, Iain McCulloch, Joseph McDouall, Sergey Ponomarenko, Jenny Nelson and Ji-Seon Kim DOI: 10.1039/c4fd90050B Justin Hodgkiss opened the discussion of the paper by Jenny Nelson: A viable explanation for the initial long-range charge separation step in organic photo- voltaic cells is via extremely high non-equilibrium charge mobilities of charge pairs initially formed high in the density of states (DOS). In this model, charge separation would be enhanced by some degree of disorder, including possibly the disorder induced by the packing with the fullerene at the heterojunction. Can you comment on the implications of your work on this model of charge separation? Do you see sufficient disorder higher in the DOS to expect high initial hole mobilities? Jenny Nelson answered: The effect of enhanced disorder near the interfaces in driving charge away from the interfaces towards regions where the materials are more ordered and the electronic states lie deeper into the band gap seems a very plausible one to me. The model would be compatible with this because the deeper lying states result from more extended regions of conjugation that would be more likely to occur away from the interfaces, where the second material in a hetero- junction is less able to disrupt packing. In the work done so far, we concentrated mainly on the polymer domain and so were not able to study the interfaces in detail. The model could however be applied to binary systems, and this effect of a destabilisation of the electronic states due to packing disorder close to the interface could be studied. The limiting factor will be the time taken to carry out molecular dynamics (MD) of many representative binary systems. Donal Bradley queried: Did you assume that the P3HT polymer is 100% regioregular and, if so, what will happen if you consider a non-regioregular polymer structure? This journal is © The Royal Society of Chemistry 2014 Faraday Discuss. , 2014, 174, 341–355 | 341 Faraday Discussions Cite this: Faraday Discuss. , 2014, 174, 341 DISCUSSIONS Published on 18 November 2014. Downloaded on 06/03/2015 14:56:00. View Article Online View Journal | View Issue