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)(2)PbI(4) 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)(2)PbI(4) films grown on strained epitaxial MAPbI(3) 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)(2)PbI(4) RP films and stable 2D/3D heterostructures.