title: Defect-Induced Band-Edge Reconstruction of a Bismuth-Halide Double Perovskite for Visible-Light Absorption.
abstract: Halide double perovskites have recently been developed as less toxic analogs of the lead perovskite solar-cell absorbers APbX3(A = monovalent cation; X = Br or I). However, all known halide double perovskites have large bandgaps that afford weak visible-light absorption. The first halide double perovskite evaluated as an absorber, Cs2AgBiBr6(1), has a bandgap of 1.95 eV. Here, we show that dilute alloying decreases 1's bandgap by ca. 0.5 eV. Importantly, time-resolved photoconductivity measurements reveal long-lived carriers with microsecond lifetimes in the alloyed material, which is very promising for photovoltaic applications. The alloyed perovskite described herein is the first double perovskite to show comparable bandgap energy and carrier lifetime to those of (CH3NH3)PbI3. By describing how energy- and symmetry-matched impurity orbitals, at low concentrations, dramatically alter 1's band edges, we open a potential pathway for the large and diverse family of halide double perovskites to compete with APbX3absorbers.
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Adam H
authors.initials: AH
authors.lastname: Slavney
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Physics, University of California Berkeley , Berkeley, California 94720, United States.
authors.forename: Linn
authors.initials: L
authors.lastname: Leppert
authors.affiliation: Optoelectronic Materials Section, Department of Chemical Engineering, Delft University of Technology , 2628CD Delft, The Netherlands.|Materials Innovation Institute (M2i) , 2628CD Delft, The Netherlands.
authors.forename: Davide
authors.initials: D
authors.lastname: Bartesaghi
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.|Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Aryeh
authors.initials: A
authors.lastname: Gold-Parker
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Michael F
authors.identifier: http://orcid.org/0000-0002-7513-1166
authors.initials: MF
authors.lastname: Toney
authors.affiliation: Optoelectronic Materials Section, Department of Chemical Engineering, Delft University of Technology , 2628CD Delft, The Netherlands.
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Savenije
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Physics, University of California Berkeley , Berkeley, California 94720, United States.|Kavli Energy NanoScience, Institute at Berkeley , Berkeley, California 94720, United States.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Neaton
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Hemamala I
authors.identifier: http://orcid.org/0000-0003-4949-8068
authors.initials: HI
authors.lastname: Karunadasa