Intermolecular Interactions of A‑Site Cations Modulate Stability of 2D Metal Halide Perovskites

Controlling the chemical properties of A-site cations in 2D metal halide perovskites (MHPs) and in 2D/3D assemblies is key to stable and efficient optoelectronic devices. Here, we rationalize the chemical interactions of different classes of organic cations in 2D MHPs, which are responsible for material stability in 2D and 2D/3D heterojunctions. Our results emphasize potential enhancement in stability by hydrogen bonding within the organic framework, showing substantially stronger intermolecular interaction compared to aromatic π–π stacking and aliphatic chains. This observation may lead to the design of organic cations with enhanced intermolecular interactions for increased stability in MHP-based devices.