The Effect of Strain on Ion Migration in Metal Halide Perovskites
Bruno Ehrler a
a Center for Nanophotonics, AMOLF, Amsterdam, The Netherlands, Science Park 104, Amsterdam, Netherlands
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
Invited Speaker, Bruno Ehrler, presentation 036
Publication date: 20th April 2022

Ion migration is one of the main mechanisms for degradation and dynamic changes during the operation of perovskite devices. These undesirable effects need to be suppressed for large-scale commercialization.

For example, ion migration leads to phase segregation in mixed-halide perovskites. By applying pressure, we show that compressive strain can reduce phase segregation. The reduction comes from an increase in the activation energy for ion migration, which slows down the phase segregation[1]. Perhaps more importantly, strain also affects the thermodynamics of the mixed and de-mixed perovskite phases. At high compressive strain the thermodynamically stable phase is more mixed then at ambient pressure[2].

While applying pressure is impractical to stabilize real devices, we also show that compositional engineering can have a similar effect. For example, using a smaller cation leads to shrinkage of the lattice which also reduces ion migration. Other compositional differences that affect the ion migration are the mixing ratio of halides[3], and the application of 2D perovskite layers. I will show initial results on the reduction of ion migration when introducing these 2D layers, even though it is not yet clear if the reduction of ion migration stems from strain effects or steric hindrance.

Overall, understanding effect of structural changes on ion migration, and hence on intrinsic material stability, is crucial to stabilize perovskite devices for many decades under operation.

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