Interfacial fracture of hybrid organic–inorganic perovskite solar cells

The interfacial robustness of perovskite solar cells (PSCs) is important due to the potential for failure resulting from applied loads or deformation in devices that are fabricated on rigid or flexible substrates, and/or residual stresses due to thermal expansion mismatch between layers. Since these can occur across any of the interfaces within typical hybrid organic–inorganic perovskite solar cells, we explore the mechanisms of interfacial fracture between the layered structures of model hybrid organic–inorganic perovskite solar cells. Brazil disk interfacial fracture specimens enable studies of the mode-mixity dependence of interfacial fracture toughness for each interface. The robustness of interfaces is studied across a range of mode mixities between pure mode I and pure mode II. A combination of optical and scanning electron microscopy further elucidates the underlying crack/microstructure interactions and fracture modes. These reveal crack-tip shielding due to crack bridging and microcracking, which were modeled using a zone shielding model to predict the mode-mixity dependence of the interfacial fracture toughness values. We discuss the implications for the development of hybrid organic–inorganic perovskite solar cells with robust interfaces for scalable deployment of photovoltaics.