posted on 2023-11-24, 00:37authored byJohannes L. Teunissen, Tom Braeckevelt, Irina Skvortsova, Jinhui Guo, Bapi Pradhan, Elke Debroye, Maarten B. J. Roeffaers, Johan Hofkens, Sandra Van Aert, Sara Bals, Sven M. J. Rogge, Veronique Van Speybroeck
CsPbI3 is a promising perovskite material
for photovoltaic
applications in its photoactive perovskite or black phase. However,
the material degrades to a photovoltaically inactive or yellow phase
at room temperature. Various mitigation strategies are currently being
developed to increase the lifetime of the black phase, many of which
rely on inducing strains in the material that hinder the black-to-yellow
phase transition. Physical insight into how these strategies exactly
induce strain as well as knowledge of the spatial extent over which
these strains impact the material is crucial to optimize these approaches
but is still lacking. Herein, we combine machine learning potential-based
molecular dynamics simulations with our in silico strain engineering
approach to accurately quantify strained large-scale atomic structures
on a nanosecond time scale. To this end, we first model the strain
fields introduced by atomic substitutions as they form the most elementary
strain sources. We demonstrate that the magnitude of the induced strain
fields decays exponentially with the distance from the strain source,
following a decay rate that is largely independent of the specific
substitution. Second, we show that the total strain field induced
by multiple strain sources can be predicted to an excellent approximation
by summing the strain fields of each individual source. Finally, through
a case study, we illustrate how this additive character allows us
to explain how complex strain fields, induced by spatially extended
strain sources, can be predicted by adequately combining the strain
fields caused by local strain sources. Hence, the strain additivity
proposed here can be adopted to further our insight into the complex
strain behavior in perovskites and to design strain from the atomic
level onward to enhance their sought-after phase stability.