title: Ionic polarization-induced current-voltage hysteresis in CH3NH3PbX3 perovskite solar cells.
abstract: CH3NH3PbX3 (MAPbX3) perovskites have attracted considerable attention as absorber materials for solar light harvesting, reaching solar to power conversion efficiencies above 20%. In spite of the rapid evolution of the efficiencies, the understanding of basic properties of these semiconductors is still ongoing. One phenomenon with so far unclear origin is the so-called hysteresis in the current-voltage characteristics of these solar cells. Here we investigate the origin of this phenomenon with a combined experimental and computational approach. Experimentally the activation energy for the hysteretic process is determined and compared with the computational results. First-principles simulations show that the timescale for MA(+) rotation excludes a MA-related ferroelectric effect as possible origin for the observed hysteresis. On the other hand, the computationally determined activation energies for halide ion (vacancy) migration are in excellent agreement with the experimentally determined values, suggesting that the migration of this species causes the observed hysteretic behaviour of these solar cells.
authors: Laboratoire de Chimie et Biochimie Computationnelles, ISIC, FSB-BCH, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland.|National Competence Center of Research (NCCR) MARVEL-Materials' Revolution: Computational Design and Discovery of Novel Materials, Lausanne CH-1015, Switzerland.
authors: Simone
authors: S
authors: Meloni
authors: Laboratory of Photonics and Interfaces, ISIC, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Thomas
authors: T
authors: Moehl
authors: Laboratory of Photonics and Interfaces, ISIC, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.|Group for Molecular Engineering of Functional Materials, ISIC-Valais, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Wolfgang
authors: W
authors: Tress
authors: Laboratory of Photonics and Interfaces, ISIC, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.|Center for Physical Sciences and Technology, Savanorių Avenue 231, Vilnius LT-02300, Lithuania.
authors: Marius
authors: M
authors: Franckevičius
authors: Group for Molecular Engineering of Functional Materials, ISIC-Valais, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Michael
authors: M
authors: Saliba
authors: Group for Molecular Engineering of Functional Materials, ISIC-Valais, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Yong Hui
authors: YH
authors: Lee
authors: Group for Molecular Engineering of Functional Materials, ISIC-Valais, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Peng
authors: http://orcid.org/0000-0002-4963-2282
authors: P
authors: Gao
authors: Group for Molecular Engineering of Functional Materials, ISIC-Valais, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Mohammad Khaja
authors: MK
authors: Nazeeruddin
authors: Laboratory of Photonics and Interfaces, ISIC, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Shaik Mohammed
authors: SM
authors: Zakeeruddin
authors: Laboratoire de Chimie et Biochimie Computationnelles, ISIC, FSB-BCH, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland.|National Competence Center of Research (NCCR) MARVEL-Materials' Revolution: Computational Design and Discovery of Novel Materials, Lausanne CH-1015, Switzerland.
authors: Ursula
authors: U
authors: Rothlisberger
authors: Laboratory of Photonics and Interfaces, ISIC, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
authors: Michael
authors: M
authors: Graetzel