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Speaker: Loreta Muscarella BSc - AMOLF

Title: Pressure-induced compression to manipulate phase segregation in mixed-halide perovskites

Abstract: Metal halide perovskite semiconductors have recently received tremendous attention in materials science, as these yielded highly efficient solar cells and LEDs. Mixing halides is an effective strategy to obtain any desired absorption onset or emission energy in the visible. A major drawback of these mixed-halide perovskites is that under illumination, the halides segregate into iodide- and bromide-rich domains. As a result, the bandgap is no longer homogeneous and light emission mainly occurs from the lowest-bandgap domains. In this talk, I will present how compression of mixed-halide perovskites increases the stability against halide segregation. Using unique pressure-dependent transient absorption spectroscopy, we found that the segregation in mixed-halide perovskites is substantially retarded at external pressures of 3000 bar. We observed that the stability against halide segregation can also be improved at ambient conditions by chemical compression of the perovskite, via partial replacement of the cations with smaller ones. We argue that the enhanced stability at high pressure is related to an increase in the activation barrier (kinetics) for segregation as well as improved thermodynamic stability. Finally, I will give a perspective on the long-term stability of mixed-halide perovskites, which would be essential for any application of perovskites requiring tunable and stable emission energies.