Improved Mechanical Adhesion and Durability Enabled by Bilayer Hole Transport Layers in Perovskite Solar Cells

We investigate the mechanical integrity of various types of self-assembled monolayers (SAMs) and NiOx and metal halide perovskite half-cells incorporating these hole transport layers (HTLs). Through macroscopic and microscopic techniques, we quantify interfacial fracture energies (Gc) and identify failure points within device stacks susceptible to delamination. Importantly, our results reveal a significant improvement in mechanical reliability through significantly improved Gc when a SAM is deposited on NiOx. Additionally, the use of solution-processed perovskite on NiOx layers that have low internal bonding compared to fully evaporated material stacks maintains the enhanced mechanical robustness for the overall stack. These findings underscore the role of NiOx in reinforcing interfacial adhesion within perovskites and provide valuable insights into the design of mechanically robust perovskite solar cells.