Compositional and orientational control in metal halide perovskites of reduced dimensionality

Reduced-dimensional metal halide perovskites (RDPs) have attracted significant attention in recent years due to their promising light harvesting and emissive properties. We sought to increase the systematic understanding of how RDPs are formed. Here we report that layered intermediate complexes formed with the solvent provide a scaffold that facilitates the nucleation and growth of RDPs during annealing, as observed via in situ X-ray scattering. Transient absorption spectroscopy of RDP single crystals and films enables the identification of the distribution of quantum well thicknesses. These insights allow us to develop a kinetic model of RDP formation that accounts for the experimentally observed size distribution of wells. RDPs exhibit a thickness distribution (with sizes that extend above n = 5) determined largely by the stoichiometric proportion between the intercalating cation and solvent complexes. The results indicate a means to control the distribution, composition and orientation of RDPs via the selection of the intercalating cation, the solvent and the deposition technique. A systematic analysis is performed to reveal how deposition conditions and the use of cations and solvents affect the composition and orientation of 2D and quasi-2D metal halide perovskites in thin films.