Evaluation of time dependent mechanical properties through nanoindentation of different compositions of 2D Ruddlesden Popper and 3D lead halide perovskites

Hybrid organic-inorganic perovskite (HOIPs) films' simplicity in manufacturing, both in solution and at low temperatures, foresees its application in deformable technologies including flexible photovoltaics, sensors and displays. The next generation of flexible optoelectronic devices may be possible owing to the special charac-teristics of hybrid organic-inorganic perovskites (HOIPs). However, it is necessary to have a thorough knowledge of the mechanical response of hybrid organic-inorganic perovskites(HOIPs) to dynamic strain to successfully use them in deformable devices. In the current study, a range of perovskites: 3D, butylammonium(BA) based 2D and quasi-2D, phenylethylammonium(PEA) based 2D and quasi-2D perovskite have been fabricated with particle sizes ranging in 5-10 nm as found using TEM. The nanoindentation creep and stress relaxation experiments prove the time and rate-dependent mechanical properties of this 2D, quasi-2D, and 3D HOIPs crystal though varying in their magnitudes. We observe that the 3D as well as BA based perovskite show strain rate sensitivity whereas PEA based perovskite samples were relatively insensitive towards the rate of loading. Propagation and interaction of dislocation are much more difficult in PEA-based perovskite, which has a triclinic crystal structure and are less symmetrical as compared to the BA based and 3D perovskite orthorhombic and tetragonal structure respectively. The knowledge offered by this work is crucial for creating perovskite devices that can endure mechanical deformations.