Unraveling the elastic properties of (quasi)2D hybrid perovskites: A joint experimental and theoretical study

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

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The unique properties of hybrid organic-inorganic perovskites (HOIPs) promise to open doors to next-generation flexible opto-electronic 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 nano-indentation (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 calculation to accurately model the system. Our results reveal a non-monotonic 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 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 π interactions in organic bilayers can have a determining role on 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 & Interfaces
Issue number15
StatePublished - Mar 19 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: M.A.R’s work was supported by his appointment to the Intelligence Community Postdoctoral Research Fellowship Program at Princeton University, administered by Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the Office of the Director of National Intelligence. Y.-L.L. acknowledges the financial support from NSF CMMI 1824674 and CMMI 1537011. P. T. acknowledges support from the China Scholarship Council. A. K. acknowledges support from the National Science Foundation under grant number DMR-1719353. A. M. R. acknowledges support from the Office of Naval Research, under grant number N00014- 17-1-2574. The authors also acknowledge computational support from the High-Performance Computing Modernization Office of the Department of Defense. OMB, AZ, and WP acknowledge the financial support of KAUST.


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