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| Conference Presentation | PUBDB-2026-00370 |
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2025
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Please use a persistent id in citations: doi:10.29363/nanoge.perfunpro.2025.038
Abstract: Hybrid organic-inorganic perovskites tend to undergo several structural transformations that can be caused by temperature, humidity and light. One of the striking is light-induced halide phase segregation in mixed lead-halide perovskites, i.e., formation of I-rich and Br-rich domains by the illumination with visible light [1]. This effect influences the homogeneity of the chemical composition of the mixed perovskite phase, influence the band gaps and therefore it has strong impact on the perovskite-based photovoltaic devices. Several microscopic mechanisms have been proposed to explain this effect, but the full understanding is yet to be obtained [2].In this work, we used X-ray photon correlation spectroscopy (XPCS) [3], to perform time-resolved studies of the light-induced phase segregation in (CH3NH3)PbBr1.8I1.2 [4] and track the formation of pure (CH3NH3)PbBrI3 and (CH3NH3)PbI3. This was done by observing the (001) diffraction peak from the cubic perovskite lattice and, specifically, quantifying the dynamics of coherent speckles originating from domains with different halide concentration.We observe that the phase segregation is characterized by three distinct time scales corresponding to the rapid formation of small seeds of the I-rich phase, fluctuations of the ion distribution around the quasi-equilibrium state (dynamics), and a directional drift of the ions within the crystal grains (kinetics). We also investigate a series of samples with interstitials and vacancies in the halide sublattice [5] and observe the influence of defects in the halide sublattice on phase separation. We find that samples with interstitial halides exhibit slower phase separation as samples with vacancies in the halide sublattice.
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