title: Optical analysis of CH3NH3SnxPb1-xI3absorbers: a roadmap for perovskite-on-perovskite tandem solar cells.
abstract: Organic-inorganic perovskite structures in which lead is substituted by tin are exceptional candidates for broadband light absorption. Herein we present a thorough analysis of the optical properties of CH3NH3SnxPb1-xI3films, providing the field with definitive insights about the possibilities of these materials for perovskite solar cells of superior efficiency. We report a user's guide based on the first set of optical constants obtained for a series of tin/lead perovskite films, which was only possible to measure due to the preparation of optical quality thin layers. According to the Shockley-Queisser theory, CH3NH3SnxPb1-xI3compounds promise a substantial enhancement of both short circuit photocurrent and power conversion efficiency in single junction solar cells. Moreover, we propose a novel tandem architecture design in which both top and bottom cells are made of perovskite absorbers. Our calculations indicate that such perovskite-on-perovskite tandem devices could reach efficiencies over 35%. Our analysis serves to establish the first roadmap for this type of cells based on actual optical characterization data. We foresee that this study will encourage the research on novel near-infrared perovskite materials for photovoltaic applications, which may have implications in the rapidly emerging field of tandem devices.
authors: Institute of Materials Science of Seville , Spanish National Research Council-University of Seville , Américo Vespucio 49 , 41092 , Seville , Spain . Email: h.miguez@csic.es.
authors: Miguel
authors: M
authors: Anaya
authors: Laboratory for Photomolecular Science , Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne , CH-1015-Lausanne , Switzerland . Email: juan.correa@epfl.ch.
authors: Juan P
authors: JP
authors: Correa-Baena
authors: Institute of Materials Science of Seville , Spanish National Research Council-University of Seville , Américo Vespucio 49 , 41092 , Seville , Spain . Email: h.miguez@csic.es.
authors: Gabriel
authors: G
authors: Lozano
authors: Laboratory for Photonics and Interfaces , Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne , CH-1015-Lausanne , Switzerland.
authors: Michael
authors: M
authors: Saliba
authors: Institute of Materials Science of Seville , Spanish National Research Council-University of Seville , Américo Vespucio 49 , 41092 , Seville , Spain . Email: h.miguez@csic.es.
authors: Pablo
authors: P
authors: Anguita
authors: Adolphe Merkle Institute , Chemin des Verdiers 4 , CH-1700 Fribourg , Switzerland.
authors: Bart
authors: B
authors: Roose
authors: Laboratory for Photonics and Interfaces , Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne , CH-1015-Lausanne , Switzerland.
authors: Antonio
authors: A
authors: Abate
authors: Adolphe Merkle Institute , Chemin des Verdiers 4 , CH-1700 Fribourg , Switzerland.
authors: Ullrich
authors: U
authors: Steiner
authors: Laboratory for Photonics and Interfaces , Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne , CH-1015-Lausanne , Switzerland.
authors: Michael
authors: M
authors: Grätzel
authors: Institute of Materials Science of Seville , Spanish National Research Council-University of Seville , Américo Vespucio 49 , 41092 , Seville , Spain . Email: h.miguez@csic.es.
authors: Mauricio E
authors: ME
authors: Calvo
authors: Laboratory for Photomolecular Science , Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne , CH-1015-Lausanne , Switzerland . Email: juan.correa@epfl.ch.
authors: Anders
authors: A
authors: Hagfeldt
authors: Institute of Materials Science of Seville , Spanish National Research Council-University of Seville , Américo Vespucio 49 , 41092 , Seville , Spain . Email: h.miguez@csic.es.
authors: Hernán
authors: H
authors: Míguez