Two-dimensional electronic spectroscopy reveals ultrafast dynamics at a conical intersection in an organic photovoltaic materialEphraim Sommer, Antonietta De Sio, Elena Mena-Osteritz, Peter Bäuerle and Christoph LienauEPJ Web Conf., 205 (2019) 06014DOI: https://doi.org/10.1051/epjconf/201920506014