title: The fate of electron-hole pairs in polymer:fullerene blends for organic photovoltaics.
abstract: There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs-whether they will dissociate to free charges or geminately recombine-is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%.
authors: Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.
authors: Martina
authors: M
authors: Causa'
authors: Photochemical Dynamics Group, Institute of Chemical Sciences &Engineering and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne (EPFL), SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland.
authors: Jelissa
authors: J
authors: De Jonghe-Risse
authors: Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.|Photochemical Dynamics Group, Institute of Chemical Sciences &Engineering and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne (EPFL), SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland.
authors: Mariateresa
authors: M
authors: Scarongella
authors: Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.
authors: Jan C
authors: JC
authors: Brauer
authors: Department of Materials and Centre for Plastic Electronics, Imperial College London, Exhibition Road, London SW7 2AZ, UK.|Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
authors: Ester
authors: E
authors: Buchaca-Domingo
authors: Photochemical Dynamics Group, Institute of Chemical Sciences &Engineering and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne (EPFL), SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland.
authors: Jacques-E
authors: JE
authors: Moser
authors: Department of Materials and Centre for Plastic Electronics, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors: Natalie
authors: N
authors: Stingelin
authors: Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.
authors: Natalie
authors: 0000-0001-9181-2642
authors: N
authors: Banerji