Microstructure of Methylammonium Lead iodide Perovskite Thin Films: A Comprehensive Study of the Strain and Texture

Journal Article · 25 February 2022 · Advanced Energy Materials

DOI: https://doi.org/10.1002/aenm.202103627 · OSTI ID:1897206

Medjahed, Asma A. ^[1]; Zhou, Tao ^[2]; Alvarez Quiceno, Juan Camilo ^[3]; Dally, Pia ^[4]; Pochet, Pascal ^[1]; Schülli, Tobias U. ^[5]; Djurado, David ^[1]; Reiss, Peter ^[1]; Pouget, Stéphanie  ^[1]

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1. Univ. of Grenoble Alpes, Grenoble (France)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Universidad de Antioquia UdeA, Medellin (Colombia); Univ. of Grenoble Alpes, Grenoble (France)
4. Univ. of Versailles Saint-Quentin-en-Yvelines (France); Univ. Paris-Saclay, Gif-sur-Yvette (France)
5. European Synchrotron Radiation Facility (ESRF), Grenoble (France)

Controlling the microstructure of hybrid halide perovskite thin films is essential for optimizing their performance in optoelectronic devices. It is well established that the strain state of the perovskite layer affects its stability. Likewise, the orientation of the perovskite lattice is a determining parameter as these materials have shown pronounced anisotropies in their physical and mechanical properties. In this work, the authors focus on the understanding of the mechanisms that govern the strain and texture observed in MAPbI₃ thin films deposited on various oxide substrates. A thorough study of the evolution of the strain of the perovskite layer upon cooling down to room temperature from the crystallization temperature (100 °C) shows an essentially relaxed behavior of the perovskite layers. This result contradicts the commonly accepted hypothesis according to which MAPbI₃ layers synthesized above ambient temperature are strained due to the large mismatch in the thermal expansion coefficients of the perovskite and its substrate. The texture in MAPbI₃ layers is investigated by means of synchrotron full-field diffraction X-ray microscopy. This technique allows the direct observation of the [hh0] and [00l]-oriented domains at the origin of the observed textures, demonstrating both their twin and ferroelastic nature. The stability of the different domain orientations is investigated by DFT calculations, illustrating the determining role of the chemical environment at the film-substrate interface. PbI^2- terminated surfaces are found to favor the [hh0] orientations while for MAI-terminated ones, both [hh0] and [00l] domains are equally stabilized. The different results constitute an important step of clarification and understanding from the perspective of controlling the microstructure of perovskite layers.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: French Research Agency (ANR); USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1897206
• Journal Information: Advanced Energy Materials, Journal Name: Advanced Energy Materials Journal Issue: 19 Vol. 12; ISSN 1614-6832
• Publisher: WileyCopyright Statement
• Country of Publication: United States
• Language: English