Addressing Mechanical Instabilities in Metal Halide Perovskites

Metal halide perovskites (“perovskites”) are promising materials for next-generation optoelectronic applications, but chemical and mechanical instabilities remain barriers to widespread usage. Recent efforts in my research group have focused on understanding and addressing these instabilities through multiple complementary pathways. First, I will discuss the use of extrinsic approaches to improving the mechanical stability of perovskite thin films. I will highlight the strategy developed by my group to nanocomposite the perovskite layer with polymeric nanofibers, which can increase the cohesive fracture energy by at least 5-fold with minimal reduction in device performance. I will also discuss our recent observation from multibeam optical stress sensor (MOSS) measurements that inelastic deformation occurs in metal halide perovskites during thermal cycling. Importantly, stress hysteresis during thermal cycling occurs, which is correlated with film quality degradation. This stress hysteresis can be mitigated with the inclusion of additives which improves film stability to thermal cycling, but the overall film stress increases. This observation suggests that minimization of the stress hysteresis—not the magnitude of the residual stress—may be the most appropriate target for enhancing perovskite film stability to thermal cycling.