Ruddlesden–Popper Phases of Methylammonium-Based Two-Dimensional Perovskites with 5‑Ammonium Valeric Acid AVA₂MA_n–1Pb_nI_3n+1 with n = 1, 2, and 3

5-Ammonium valeric acid (AVA) is a frequently used additive in the preparation of lead halide perovskites. However, its microscopic role as passivating, cross-linking, or templating agent is far from clear. In this work, we provide density functional theory-based structural models for the Ruddlesden–Popper (RP) phases of AVA₂(CH₃NH₃)_n−1Pb_nI_3n+1 for n = 1, 2, and 3 and validate with experimental data on polycrystalline samples for n = 1. The structural and electronic properties of the AVA-based RP phases are compared to the ones of other linker families. In contrast to aromatic and aliphatic spacers without additional functional groups, the RP phases of AVA are characterized by the formation of a regular and stable H-bonding network between the carbonyl head groups of adjacent AVA molecules in opposite layers. Because of these additional interactions, the penetration depth of the organic layer into the perovskite sheet is reduced with direct consequences for its crystalline phase. The possibility of forming strong interlinker hydrogen bonds may lead to an enhanced thermal stability.