Local Rearrangement of Iodide Defect Structure Determines Phase Segregation Effect in Mixed Halide Perovskites
Juan F. Galisteo-López a, David O. Tiede b, Mauricio E. Calvo a, Hernán Míguez a
a Instituto de Ciencia de Materiales de Sevilla (ICMS), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, C/ Américo Vespucio 49, Sevilla, Spain
b Westfälische Wilhelms-Universität Münster, Germany, Wilhelm-Klemm-Straße, 10, Münster, Germany
Proceedings of Online International Conference on Hybrid and Organic Photovoltaics (OnlineHOPV20)
Online, Spain, 2020 May 26th - 29th
Organizers: Tracey Clarke, James Durrant, Annamaria Petrozza and Trystan Watson
Poster, Juan F. Galisteo-López, 142
Publication date: 22nd May 2020

One of the main bottlenecks for the commercialization of lead-halide perovskites (LHP) is their instability against external stimuli and in particular against illumination. In this respect a material that epitomizes such instability are mixed-halide perovskites (mLHP).Upon illumination mLHP undergo structural changes leading to the formation of I-rich regions negatively affecting the performance of photovoltaic devices and LEDs based on these materials. 

Herein we show that the conspicuous photoinduced phase segregation characteristic of these materials is primarily the result of the local and metastable rearrangement of the iodide sublattice. A local photophysical study comprising spectrally-resolved laser scanning confocal microscopy is employed to find a correlation between defect density and the dynamics of photo-induced changes, which extend far from the illuminated region. We observe that iodide rich regions evolve much faster from highly defective regions. Also, by altering the material composition, we find evidence for the interplay between iodide-related defect distribution and the intra and inter domain migration dynamics giving rise to the complexity of this process.

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