Berlin 2024 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 55: Perovskite and Photovoltaics III (joint session HL/KFM)
HL 55.8: Vortrag
Freitag, 22. März 2024, 11:30–11:45, EW 203
Halide segregation and ionic motion in lead-halide perovskites — •Francisco Peña-Camargo, Felix Lang, and Martin Stolterfoht — Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
Halide segregation is a photoinduced phenomenon observed in perovskites with multiple halides at the X site of the ABX3 lattice. The evidence shows that the photoluminescence spectrum of the mixed phase red-shifts and increases its intensity in a timescale of minutes. On the other hand, it has been proven that mobile ions are present in cells in densities around 1016 cm−3, which is sufficient to screen the internal electric field, generating, among other effects, the hysteresis in the forward and reverse JV scans. The scan-speed dependence of hysteresis suggests that mobile ions have an effect on the cell performance mostly at a determined condition when the voltage sweep matches the ionic timescales. Here, by measuring the JV characteristic at different speeds with a novel technique called fast hysteresis (FH) from 10−2 to 104 V s−1, we quantify the ionic diffusion coefficient and conclude that the ionic motion happens in the seconds to minutes timescales. Moreover, using bias-assisted charge extraction (BACE) we are able to quantify the ionic volumetric density and confirm the ionic transient timescales. Based on that experimental evidence, it is plausible to link the ionic motion to halide segregation, particularly when it comes to the timescales which appear to match very well. This is also supported by the correlation of the ionic losses with the increasing Br/I ratio in triple-cation lead-based perovskite solar cells.
Keywords: mobile ions; halide segregation; hysteresis