title: Photocurrent Spectroscopy of Perovskite Layers and Solar Cells: A Sensitive Probe of Material Degradation.
abstract: Optical absorptance spectroscopy of polycrystalline CH3NH3PbI3films usually indicates the presence of a PbI2phase, either as a preparation residue or due to film degradation, but gives no insight on how this may affect electrical properties. Here, we apply photocurrent spectroscopy to both perovskite solar cells and coplanar-contacted layers at various stages of degradation. In both cases, we find that the presence of a PbI2phase restricts charge-carrier transport, suggesting that PbI2encapsulates CH3NH3PbI3grains. We also find that PbI2injects holes into the CH3NH3PbI3grains, increasing the apparent photosensitivity of PbI2. This phenomenon, known as modulation doping, is absent in the photocurrent spectra of solar cells, where holes and electrons have to be collected in pairs. This interpretation provides insights into the photogeneration and carrier transport in dual-phase perovskites.
authors.affiliation: Institute of Physics, Czech Academy of Sciences, v. v. i. , Cukrovarnická 10, 162 00 Prague, Czech Republic.|Faculty of Electrical Engineering, Czech Technical University in Prague , Technická 2, 166 27 Prague, Czech Republic.
authors.forename: Jakub
authors.identifier: http://orcid.org/0000-0002-4222-6070
authors.initials: J
authors.lastname: Holovský
authors.affiliation: KAUST Solar Center (KSC), King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia.
authors.forename: Stefaan
authors.initials: S
authors.lastname: De Wolf
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering (IMT), École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, Neuchâtel 2000, Switzerland.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Werner
authors.affiliation: Institute of Physics, Czech Academy of Sciences, v. v. i. , Cukrovarnická 10, 162 00 Prague, Czech Republic.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Remeš
authors.affiliation: Institute of Physics, Czech Academy of Sciences, v. v. i. , Cukrovarnická 10, 162 00 Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Müller
authors.affiliation: Institute of Physics, Czech Academy of Sciences, v. v. i. , Cukrovarnická 10, 162 00 Prague, Czech Republic.
authors.forename: Neda
authors.initials: N
authors.lastname: Neykova
authors.affiliation: Institute of Physics, Czech Academy of Sciences, v. v. i. , Cukrovarnická 10, 162 00 Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Ledinský
authors.affiliation: Faculty of Electrical Engineering, Czech Technical University in Prague , Technická 2, 166 27 Prague, Czech Republic.
authors.forename: Ladislava
authors.initials: L
authors.lastname: Černá
authors.affiliation: Faculty of Electrical Engineering, Czech Technical University in Prague , Technická 2, 166 27 Prague, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Hrzina
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering (IMT), École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, Neuchâtel 2000, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Löper
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering (IMT), École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, Neuchâtel 2000, Switzerland.
authors.forename: Bjoern
authors.initials: B
authors.lastname: Niesen
authors.affiliation: Photovoltaics and Thin-Film Electronics Laboratory, Institute of Microengineering (IMT), École Polytechnique Fédérale de Lausanne (EPFL) , Rue de la Maladière 71b, Neuchâtel 2000, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Ballif