title: A mixed-cation lead mixed-halide perovskite absorber for tandem solar cells.
abstract: Metal halide perovskite photovoltaic cells could potentially boost the efficiency of commercial silicon photovoltaic modules from ∼20 toward 30% when used in tandem architectures. An optimum perovskite cell optical band gap of ~1.75 electron volts (eV) can be achieved by varying halide composition, but to date, such materials have had poor photostability and thermal stability. Here we present a highly crystalline and compositionally photostable material, [HC(NH2)2](0.83)Cs(0.17)Pb(I(0.6)Br(0.4))3, with an optical band gap of ~1.74 eV, and we fabricated perovskite cells that reached open-circuit voltages of 1.2 volts and power conversion efficiency of over 17% on small areas and 14.7% on 0.715 cm(2) cells. By combining these perovskite cells with a 19%-efficient silicon cell, we demonstrated the feasibility of achieving >25%-efficient four-terminal tandem cells.
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: David P
authors.initials: DP
authors.lastname: McMeekin
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Golnaz
authors.initials: G
authors.lastname: Sadoughi
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Waqaas
authors.initials: W
authors.lastname: Rehman
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Giles E
authors.initials: GE
authors.lastname: Eperon
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Saliba
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Maximilian T
authors.initials: MT
authors.lastname: Hörantner
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Amir
authors.initials: A
authors.lastname: Haghighirad
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Nobuya
authors.initials: N
authors.lastname: Sakai
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Institute for Silicon Photovoltaics, Kekuléstrasse 5, 12489 Berlin, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Korte
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Institute for Silicon Photovoltaics, Kekuléstrasse 5, 12489 Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Rech
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Johnston
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Herz
authors.affiliation: Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith