title: The Role of Oxygen in the Degradation of Methylammonium Lead Trihalide Perovskite Photoactive Layers.
abstract: In this paper we report on the influence of light and oxygen on the stability of CH3 NH3 PbI3 perovskite-based photoactive layers. When exposed to both light and dry air the mp-Al2 O3 /CH3 NH3 PbI3 photoactive layers rapidly decompose yielding methylamine, PbI2 , and I2 as products. We show that this degradation is initiated by the reaction of superoxide (O2 (-) ) with the methylammonium moiety of the perovskite absorber. Fluorescent molecular probe studies indicate that the O2 (-) species is generated by the reaction of photoexcited electrons in the perovskite and molecular oxygen. We show that the yield of O2 (-) generation is significantly reduced when the mp-Al2 O3 film is replaced with an mp-TiO2 electron extraction and transport layer. The present findings suggest that replacing the methylammonium component in CH3 NH3 PbI3 to a species without acid protons could improve tolerance to oxygen and enhance stability.
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom).
authors.forename: Nicholas
authors.initials: N
authors.lastname: Aristidou
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom).
authors.forename: Irene
authors.initials: I
authors.lastname: Sanchez-Molina
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom).
authors.forename: Thana
authors.initials: T
authors.lastname: Chotchuangchutchaval
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom).
authors.forename: Michael
authors.initials: M
authors.lastname: Brown
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom).
authors.forename: Luis
authors.initials: L
authors.lastname: Martinez
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom).
authors.forename: Thomas
authors.initials: T
authors.lastname: Rath
authors.affiliation: Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom). s.a.haque@imperial.ac.uk.
authors.forename: Saif A
authors.initials: SA
authors.lastname: Haque
keywords: methylammonium lead triiodide; perovskites; solar cells; spectroscopy; stability