title: 8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer.
abstract: In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Förster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.
authors.affiliation: 1] IMEC, Kapeldreef 75, Leuven B-3001, Belgium [2] ESAT, KU Leuven, Kasteelpark Arenberg 10, Leuven B-3001, Belgium.
authors.forename: Kjell
authors.initials: K
authors.lastname: Cnops
authors.affiliation: 1] IMEC, Kapeldreef 75, Leuven B-3001, Belgium [2] Department of Electrical Engineering and the Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Barry P
authors.initials: BP
authors.lastname: Rand
authors.affiliation: IMEC, Kapeldreef 75, Leuven B-3001, Belgium.
authors.forename: David
authors.initials: D
authors.lastname: Cheyns
authors.affiliation: IMEC, Kapeldreef 75, Leuven B-3001, Belgium.
authors.forename: Bregt
authors.initials: B
authors.lastname: Verreet
authors.affiliation: 1] IMEC, Kapeldreef 75, Leuven B-3001, Belgium [2] ESAT, KU Leuven, Kasteelpark Arenberg 10, Leuven B-3001, Belgium.
authors.forename: Max A
authors.initials: MA
authors.lastname: Empl
authors.affiliation: 1] IMEC, Kapeldreef 75, Leuven B-3001, Belgium [2] ESAT, KU Leuven, Kasteelpark Arenberg 10, Leuven B-3001, Belgium.
authors.forename: Paul
authors.initials: P
authors.lastname: Heremans
mesh_terms: D000465:Algorithms; D011211:Electric Power Supplies; D004735:Energy Transfer; D031541:Fluorescence Resonance Energy Transfer; D037741:Fullerenes / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D054833:Isoindoles; D049449:Luminescence; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry*; D012993:Solar Energy; D013053:Spectrophotometry / Q000379:methods
chemical_list: D037741:Fullerenes; D007211:Indoles; D054833:Isoindoles; D009930:Organic Chemicals; C013647:phthalocyanine