Oriented 2D Ruddlesden-Popper metal halides by pulsed laser deposition

Two-dimensional (2D) Ruddlesden-Popper (RP) metal halides present unique and tunable properties. However, direct and oriented synthesis is challenging due to low formation energies that lead to rapid, uncontrolled growth during solution-based processing. Here, we report the solvent-free growth of oriented n = 1 (PEA)₂PbI₄ RP films by pulsed laser deposition (PLD). In situ photoluminescence (PL) during deposition reveals the formation of the n = 1 phase at the early stages of growth. X-ray diffraction (XRD) and grazing-incidence wide-angle scattering (GIWAXS) confirm a single oriented n = 1 phase, independent of the substrate. Co-localized spatially resolved PL and AFM further validate the conformal growth. While oriented growth is substrate-independent, film stability is not. (PEA)₂PbI₄ films grown on strained epitaxial MAPbI₃ remain stable for over 184 days without any sign of cation exchange. This work highlights the potential of PLD for direct, room-temperature synthesis of 2D (PEA)₂PbI₄ RP films and stable 2D/3D heterostructures.