title: Reduced voltage losses yield 10% efficient fullerene free organic solar cells with >1 V open circuit voltages.
abstract: Optimization of the energy levels at the donor-acceptor interface of organic solar cells has driven their efficiencies to above 10%. However, further improvements towards efficiencies comparable with inorganic solar cells remain challenging because of high recombination losses, which empirically limit the open-circuit voltage (Voc) to typically less than 1 V. Here we show that this empirical limit can be overcome using non-fullerene acceptors blended with the low band gap polymer PffBT4T-2DT leading to efficiencies approaching 10% (9.95%). We achieveVocup to 1.12 V, which corresponds to a loss of onlyEg/q-Voc= 0.5 ± 0.01 V between the optical bandgapEgof the polymer andVoc. This highVocis shown to be associated with the achievement of remarkably low non-geminate and non-radiative recombination losses in these devices. Suppression of non-radiative recombination implies high external electroluminescence quantum efficiencies which are orders of magnitude higher than those of equivalent devices employing fullerene acceptors. Using the balance between reduced recombination losses and good photocurrent generation efficiencies achieved experimentally as a baseline for simulations of the efficiency potential of organic solar cells, we estimate that efficiencies of up to 20% are achievable if band gaps and fill factors are further optimized.
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk; IEK5-Photovoltaics , Forschungszentrum Jülich , 52425 Jülich , Germany . Email: t.kirchartz@fz-juelich.de.
authors.forename: D
authors.initials: D
authors.lastname: Baran
authors.affiliation: IEK5-Photovoltaics , Forschungszentrum Jülich , 52425 Jülich , Germany . Email: t.kirchartz@fz-juelich.de; Faculty of Engineering and CENIDE , University of Duisburg-Essen , Carl-Benz-Straße 199 , 47057 Duisburg , Germany.
authors.forename: T
authors.initials: T
authors.lastname: Kirchartz
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk.
authors.forename: S
authors.initials: S
authors.lastname: Wheeler
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk.
authors.forename: S
authors.initials: S
authors.lastname: Dimitrov
authors.affiliation: King Abdullah University of Science and Technology (KAUST) , KSC , Thuwal 23955-6900 , Saudi Arabia.
authors.forename: M
authors.initials: M
authors.lastname: Abdelsamie
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk.
authors.forename: J
authors.initials: J
authors.lastname: Gorman
authors.affiliation: King Abdullah University of Science and Technology (KAUST) , KSC , Thuwal 23955-6900 , Saudi Arabia.
authors.forename: R S
authors.initials: RS
authors.lastname: Ashraf
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk.
authors.forename: S
authors.initials: S
authors.lastname: Holliday
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk.
authors.forename: A
authors.initials: A
authors.lastname: Wadsworth
authors.affiliation: Institute of Materials for Electronics and Energy Technology (I-MEET) , Friedrich-Alexander-University Erlangen-Nuremberg , Erlangen , Germany.
authors.forename: N
authors.initials: N
authors.lastname: Gasparini
authors.affiliation: IEK5-Photovoltaics , Forschungszentrum Jülich , 52425 Jülich , Germany . Email: t.kirchartz@fz-juelich.de.
authors.forename: P
authors.initials: P
authors.lastname: Kaienburg
authors.affiliation: Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology , Clear Water Bay , Kowloon , Hong Kong , China.
authors.forename: H
authors.initials: H
authors.lastname: Yan
authors.affiliation: King Abdullah University of Science and Technology (KAUST) , KSC , Thuwal 23955-6900 , Saudi Arabia.
authors.forename: A
authors.initials: A
authors.lastname: Amassian
authors.affiliation: Institute of Materials for Electronics and Energy Technology (I-MEET) , Friedrich-Alexander-University Erlangen-Nuremberg , Erlangen , Germany.
authors.forename: C J
authors.initials: CJ
authors.lastname: Brabec
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk.
authors.forename: J R
authors.initials: JR
authors.lastname: Durrant
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics , Imperial College London , London , SW7 2AZ , UK . Email: d.baran@imperial.ac.uk; King Abdullah University of Science and Technology (KAUST) , KSC , Thuwal 23955-6900 , Saudi Arabia.
authors.forename: I
authors.initials: I
authors.lastname: McCulloch