title: Not All That Glitters Is Gold: Metal-Migration-Induced Degradation in Perovskite Solar Cells.
abstract: Perovskite solar cells (PSCs) have now achieved efficiencies in excess of 22%, but very little is known about their long-term stability under thermal stress. So far, stability reports have hinted at the importance of substituting the organic components, but little attention has been given to the metal contact. We investigated the stability of state-of-the-art PSCs with efficiencies exceeding 20%. Remarkably, we found that exposing PSCs to a temperature of 70 °C is enough to induce gold migration through the hole-transporting layer (HTL), spiro-MeOTAD, and into the perovskite material, which in turn severely affects the device performance metrics under working conditions. Importantly, we found that the main cause of irreversible degradation is not due to decomposition of the organic and hybrid perovskite layers. By introducing a Cr metal interlayer between the HTL and gold electrode, high-temperature-induced irreversible long-term losses are avoided. This key finding is essential in the quest for achieving high efficiency, long-term stable PSCs which, in order to be commercially viable, need to withstand hard thermal stress tests.
authors.forename: Konrad
authors.initials: K
authors.lastname: Domanski
authors.forename: Juan-Pablo
authors.initials: JP
authors.lastname: Correa-Baena
authors.affiliation: Laboratory for Nanoscale Materials Science, Swiss Federal Laboratories for Materials Science and Technology , CH-8600 Dübendorf, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mine
authors.affiliation: Group for Molecular Engineering of Functional Materials, Institute of Chemical Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1950 Sion, Switzerland.
authors.forename: Mohammad Khaja
authors.initials: MK
authors.lastname: Nazeeruddin
authors.affiliation: Adolphe Merkle Institute, University of Fribourg , CH-1700 Fribourg, Switzerland.
authors.forename: Antonio
authors.initials: A
authors.lastname: Abate
authors.forename: Michael
authors.initials: M
authors.lastname: Saliba
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Tress
authors.forename: Anders
authors.initials: A
authors.lastname: Hagfeldt
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
keywords: buffer layers; degradation; gold; metal electrodes; perovskite solar cells; secondary ion mass spectrometry; stability