Structural transition, phase change and degradation of CH3NH3PbI3 layers under air or vacuum

Antonino La Magna^a, Giovanni Mannino^a, Emanuele Smecca^a, Giovanna Pellegrino^a, Ioannis Deretzis^a, Alessandra Alberti^a, Nobuya Sakai^b, Tsutomu Miyasaka^b

^aCNR-IMM, zona industriale strada VIII n°5, Catania, 95121, Italy

^bToin University of Yokohama, 1614 Kurogane-cho, Aoba, Yokohama, 2258503, Japan

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Poster, Alessandra Alberti, 023
Publication date: 5th February 2015

We investigate structural transition, phase change and degradationpath of methylammonium lead iodide (MAPbI₃) films over flat TiO₂ substrates in air or vacuum conditions by means of X-Ray Diffraction, Spectroscopic Ellipsometry and the Density Functional Theory. With this combined approach, we reveal the existence of an early mechanism in the MAPbI₃ degradation process, which can be described as a purely internal structural modification of the material. This internal transformation drives the starting tetragonal lattice in the direction of a cubic atomic arrangement and implies a contraction of the c-axis length from 1.267 to 1.263 nm, without any significant change in the other lattice parameters and without producing PbI₂. The early stage is then followed by a usual phase transition with the PbI₂ amount progressively increasing at the expenses of the MAPbI₃ film. The occurrence of a precursory stage as well as the later degradation dynamics are independent of the explored storage ambient, namely air or vacuum. Based on ab initio calculations, we argue that even in the absence of humidity, a disintegration of the perovskite structure can take place through the statistical formation of neutral molecular defects, whose volatility at surfaces should break the thermodynamic defect equilibria. Although our findings can be not straightforwardly extended to all MA perovskite films that are prepared with different synthetic processes, they pose a general question about the role of the internal stability of the material in relationship with the deposition methods and procedures.
Structural transition, phase change and degradation path of a MAPbI3 film over flat TiO2 substrate.

nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.

MATSUS

Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.

International Conference on Hybrid and Organic Photovoltaics

International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.

Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics

The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.

International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics

The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.