Oriented 2D Ruddlesden-Popper Metal Halides by Pulsed Laser Deposition

Abstract: 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 and n = 1 2D $(\mbox{PEA})_2\mbox{PbI}_4$ RP films by pulsed laser deposition (PLD). In situ photoluminescence (PL) during deposition reveals formation of the n =1 phase at the ear;y 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 on strained epitaxial $\mbox{MAPbI}_3$ 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 $(\mbox{PEA})_2\mbox{PbI}_4$ RP films and stable 2D/3D heterostructures.