Tailoring the mechanical response of Ruddlesden Popper lead halide perovskites

Abstract

Two dimensional (2D) Ruddlesden Popper perovskites have been extensively studied for their exceptional optical and electronic characteristics while only a few studies have shed light on their mechanical properties. The existing literature mainly discusses the mechanical strength of single crystal perovskites, however a study of structure tunability of 2D perovskite thin films is still missing. In this study, we report the effect of number of inorganic layers ‘n’ on elastic modulus of 2D, quasi-2D perovskites and 3D perovskite thin films using nanoindentation technique. Our studies indicate the role of orientation of the inorganic layers in perovskite films in tailoring their mechanical response. The experimental results have been substantiated using first principle density functional theory (DFT) calculations. We also report other important mechanical parameters namely, shear modulus, bulk modulus, Poisson’s ratio, Pugh’s ratio, Vickers hardness, yield strength and the universal elastic anisotropic index using DFT simulations. Anisotropy is observed in the elastic modulus of the materials under study and has been discussed in detail in the manuscript. Understanding the mechanical behavior of 2D Ruddlesden Popper perovskites thin film in comparison with conventional 3D perovskite offers intriguing insights into the atomic layer dependent properties and paves the path for next generation mechanically durable and novel devices.