Out-of-Plane Mechanical Properties of 2D Hybrid Organic-Inorganic Perovskites by Nanoindentation

TL;DR

This study investigates the out-of-plane mechanical properties of 2D hybrid organic-inorganic perovskites, revealing how structural variations influence stiffness and providing insights for designing more stable and flexible photovoltaic materials.

Contribution

It provides the first systematic analysis of how organic spacer length and inorganic layer number affect the out-of-plane mechanical properties of 2D HOIPs, combining experimental and DFT simulation results.

Findings

Larger inorganic layer number (n) increases stiffness.

Shorter organic spacer molecules (R) lead to stiffer materials.

DFT simulations align with experimental measurements.

Abstract

2D layered hybrid organic-inorganic perovskites (HOIPs) have demonstrated improved stability and promising photovoltaic performance. The mechanical properties of such functional materials are both fundamentally and practically important to achieve both high performance and mechanical stable (flexible) devices. Here we report the mechanical properties of a series of 2D layered lead iodide HOIPs and investigate the role of structural sub-units (e.g., variation of the length of the organic spacer molecules -R and the number of inorganic layer -n) on the mechanical properties. While 2D HOIPs have much lower nominal elastic moduli and hardness than 3D HOIPs, larger n number and shorter R lead to stiffer materials. DFT simulations showed a similar trend to the experimental results. We compared these findings with other 2D layered crystals and shed light on routes to further tune the out-of-plane mechanical properties of 2D layered HOIPs.