title: Unravelling the low-temperature metastable state in perovskite solar cells by noise spectroscopy.
abstract: The hybrid perovskite methylammonium lead iodide CH3NH3PbI3recently revealed its potential for the manufacturing of low-cost and efficient photovoltaic cells. However, many questions remain unanswered regarding the physics of the charge carrier conduction. In this respect, it is known that two structural phase transitions, occurring at temperatures near 160 and 310 K, could profoundly change the electronic properties of the photovoltaic material, but, up to now, a clear experimental evidence has not been reported. In order to shed light on this topic, the low-temperature phase transition of perovskite solar cells has been thoroughly investigated by using electric noise spectroscopy. Here it is shown that the dynamics of fluctuations detect the existence of a metastable state in a crossover region between the room-temperature tetragonal and the low-temperature orthorhombic phases of the perovskite compound. Besides the presence of a noise peak at this transition, a saturation of the fluctuation amplitudes is observed induced by the external DC current or, equivalently, by light exposure. This noise saturation effect is independent on temperature, and may represent an important aspect to consider for a detailed explanation of the mechanisms of operation in perovskite solar cells.
authors.affiliation: Dipartimento di Fisica "E.R. Caianiello" and CNR-SPIN Salerno, Università di Salerno, I-84084 Fisciano, Salerno, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Barone
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Silizium Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Lang
authors.affiliation: Dipartimento di Fisica "E.R. Caianiello" and CNR-SPIN Salerno, Università di Salerno, I-84084 Fisciano, Salerno, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Mauro
authors.affiliation: Dipartimento di Ingegneria Industriale, Università di Salerno, I-84084 Fisciano, Salerno, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Landi
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Silizium Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Rappich
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Silizium Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany.
authors.forename: N H
authors.initials: NH
authors.lastname: Nickel
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Silizium Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Rech
authors.affiliation: Dipartimento di Fisica "E.R. Caianiello" and CNR-SPIN Salerno, Università di Salerno, I-84084 Fisciano, Salerno, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Pagano
authors.affiliation: Dipartimento di Ingegneria Industriale, Università di Salerno, I-84084 Fisciano, Salerno, Italy.
authors.forename: H C
authors.initials: HC
authors.lastname: Neitzert