Mitigating Mechanical Failure—Improving the Mechanical Robustness of Metal Halide Perovskites

We report on the mechanical properties of high-efficiency perovskite solar cells (PSCs) with different chemical components by measuring the fracture energy (G_c) of films and devices. With the help of both macroscopic and microscopic techniques, we identify the locations where fracture takes place in the devices (either adhesive or cohesive failure) with various material and device structures. We propose strategies that can improve the fracture energy of PSCs based on the measured G_c and improve the operational stability of PSCs by improving interfacial adhesion at the hole and electron-transporting layer interfaces. We also demonstrate the effect of encapsulants and how rational package design can be used to improve PSC durability from the perspective of mitigating mechanical failures. Our findings offer a pathway to rationally study the mechanical properties of PSCs and enable such cells to be more mechanically robust to reach commercial viability.