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Abstract Hybrid metal halide perovskite (MHP) materials, while being promising for photovoltaic technology, also encounter challenges related to material stability. Combining 2D MHPs with 3D MHPs offers a viable solution, yet there is a gap in the understanding of the stability among various 2D materials. The mechanical, ionic, and environmental stability of various 2D MHP ligands are reported, and an improvement with the use of a quater‐thiophene‐based organic cation (4TmI) that forms an organic‐semiconductor incorporated MHP structure is demonstrated. It is shown that the best balance of mechanical robustness, environmental stability, ion activation energy, and reduced mobile ion concentration under accelerated aging is achieved with the usage of 4TmI. It is believed that by addressing mechanical and ion‐based degradation modes using this built‐in barrier concept with a material system that also shows improvements in charge extraction and device performance, MHP solar devices can be designed for both reliability and efficiency. 

We report on the use of open-air blade-coating as a scalable method for producing metal halide perovskite films with >10× fracture energy for durability and mechanical stability through the addition of corn starch polymer additives. This results in a manufacturable and robust perovskite that has tunable thicknesses exceeding 10 µm, among the highest reported values for solution-processed polycrystalline films. We find that an increasing amount of starch causes more uniform carbon distribution within the perovskite thickness as quantified by cross-sectional elemental composition measurements. Further, the incorporation of starch introduces beneficial compressive film stresses. Importantly, the optoelectronic behavior is not compromised, as the photoluminescence spectrum becomes more homogenous with the addition of corn starch up to 20% by weight.