Unraveling the Elastic Properties of (Quasi)Two-Dimensional Hybrid Perovskites: A Joint Experimental and Theoretical Study

Marcos A. Reyes-Martinez, Peng Tan, Arvin Kakekhani, Sayan Banerjee, Ayan A. Zhumekenov, Wei Peng, Osman M. Bakr, Andrew M. Rappe, Yueh Lin Loo

Research output: Contribution to journalArticle

Abstract

The unique properties of hybrid organic-inorganic perovskites (HOIPs) promise to open doors to next-generation flexible optoelectronic devices. Before such advances are realized, a fundamental understanding of the mechanical properties of HOIPs is required. Here, we combine ab initio density functional theory (DFT) modeling with a diverse set of experiments to study the elastic properties of (quasi)2D HOIPs. Specifically, we focus on (quasi)2D single crystals of phenethylammonium methylammonium lead iodide, (PEA)2PbI4(MAPbI3)n-1, and their 3D counterpart, MAPbI3. We used nanoindentation (both Hertzian and Oliver-Pharr analyses) in combination with elastic buckling instability experiments to establish the out-of-plane and in-plane elastic moduli. The effect of Van der Waals (vdW) forces, different interlayer interactions, and finite temperature are combined with DFT calculations to accurately model the system. Our results reveal a nonmonotonic dependence of both the in-plane and out-of plane elastic moduli on the number of inorganic layers (n) rationalized by first-principles calculations. We discuss how the presence of defects in as-grown crystals and macroscopic interlayer deformations affect the mechanical response of (quasi)2D HOIPs. Comparing the in- and out-of-plane experimental results with the theory reveals that perturbations to the covalent and ionic bonds (which hold a 2D layer together) is responsible for the relative out-of-plane stiffness of these materials. In contrast, we conjecture that the in-plane softness originates from macroscopic or mesoscopic motions between 2D layers during buckling experiments. Additionally, we learn how dispersion and πinteractions in organic bilayers can have a determining role in the elastic response of the materials, especially in the out-of-plane direction. The understanding gained by comparing ab initio and experimental techniques paves the way for rational design of layered HOIPs with mechanical properties favorable for strain-intensive applications. Combined with filters for other favorable criteria, e.g., thermal or moisture stability, one can systematically screen viable (quasi)2D HOIPs for a variety of flexible optoelectronic applications.

Original languageEnglish (US)
Pages (from-to)17881-17892
Number of pages12
JournalACS Applied Materials and Interfaces
Volume12
Issue number15
DOIs
StatePublished - Apr 15 2020

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Keywords

  • density functional theory
  • elastic properties
  • flexible electronics
  • layered perovskites
  • mechanical properties
  • nanoindentation
  • two-dimensional hybrid organic-inorganic perovskites
  • wrinkling

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    Reyes-Martinez, M. A., Tan, P., Kakekhani, A., Banerjee, S., Zhumekenov, A. A., Peng, W., Bakr, O. M., Rappe, A. M., & Loo, Y. L. (2020). Unraveling the Elastic Properties of (Quasi)Two-Dimensional Hybrid Perovskites: A Joint Experimental and Theoretical Study. ACS Applied Materials and Interfaces, 12(15), 17881-17892. https://doi.org/10.1021/acsami.0c02327