π-Conjugated Donor-Acceptor Systems as Metal-Free Sensitizers for Dye-Sensitized Solar Cell ApplicationsM. Wielopolski, J.-E. Moser, M. Marszalek, S. M. Zakeeruddin and M. GrätzelEPJ Web of Conferences, 41 (2013) 08013DOI: https://doi.org/10.1051/epjconf/20134108013