Iodide Nanodomain Formation as Local Rearrangement Process during Phase Segregation in Mixed Halide Perovskites
David Otto Tiede a, Juan F. Galisteo-López a, Mauricio E. Calvo a, Hernán Miguez a
a Institute of Materials Science of Seville, (Spanish National Research Council (CSIC) – Univ. Seville), Seville, Spain
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, David Otto Tiede, presentation 144
Publication date: 20th April 2022

Photo-induced changes are among the most critical instabilities of lead-halide perovskties that hamper their future commercialization. A clear example is the reversible light-induced phase segregation and its corresponding shift in the emission wavelength, a frequently reported phenomenon hindering both efficient light-harvesting in tandem solar cells and spectral output of LEDs. However, its underlying halide migration mechanism still remains under debate. Over the recent years, various reports have pointed towards a critical role of defects in this process [1] and a strong dependency on environmental effects [2]. Most recently, nanoscale halide heterogeneities were demonstrated to dominate mixed halide perovskite performance in perovskite solar cells [3].

In this talk, we review halide reorganization mechanisms and discuss the importance of iodide defects in mixed halide perovskite phase segregation [4]. Spectrally and time resolved photoluminescence confocal studies of CH3NH3PbBrxI3-x thin films demonstrating the formation of iodine-rich nanodomains are presented. With macroscopic measurements we verify that defects account for a dominant role on phase segregation and cause the formation of iodine-rich domains in small parts of the material.  By modifying atmospheric conditions and changing the stoichiometry of the halide components during the synthesis to modify its defect structure, we determine the impact of iodide vacancies and interstitials on the photophysics of these materials.

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