Phase Segregation Effect in Mixed Halide Perovskites: The Role of the Iodide Defect Structure and its Local Rearrangement
David Tiede a, Juan F. Galisteo-López a, Mauricio E. Calvo a, Hernán Miguez a
a Institute of Materials Science of Seville, CSIC - US, Calle Américo Vespucio, 49, Sevilla, Spain
Proceedings of nanoGe Fall Meeting 2021 (NFM21)
#PerEmer21. Perovskites III: Emerging Materials and Phenomena
Online, Spain, 2021 October 18th - 22nd
Organizers: Moritz Futscher, Jovana Milic and Aditya Mohite
Poster, David Tiede, 288
Publication date: 23rd September 2021

Light-induced changes in mixed halide perovskites are among the most critical instabilities of this material that hamper future commercialization. [1] In particular, reversible light-induced phase segregation and its corresponding shift in the emission wavelength is a major drawback in precise wavelength tuning, which is crucial for both efficient light-harvesting in tandem solar cells and the spectral output of LEDs. Over the past years, various reports have pointed towards a critical role of defects in this process and a strong dependency on environmental effects. However, the exact mechanism behind the migration of halides is still under debate. [2]

In this work [3], we have carried out a spectrally-resolved confocal study of the formation of iodine-rich domains in CH3NH3PbBrxI3-x thin films. With macroscopic measurements we verify that defects account for a dominant role on phase segregation and cause the formation of iodine-rich domains in minor parts of the material.  By modifying atmospheric conditions and changing the stoichiometry of the halide components during the synthesis, we clarify the impact of vacancies and interstitials on the photophysics of these materials.

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