Layered Hybrid Lead Iodide Perovskites with Short Interlayer Distances

Layered hybrid perovskites comprise modular components that are individually highly tunable, resulting in materials with a range of structures and properties. In these layered materials, the usual assumption is of two-dimensional electronic behavior, because of the relatively large separations between the inorganic layers. Here, we report two layered hybrid lead iodide perovskites that possess unusually short interlayer distances: (IPA)(2)(MA)Pb2I7 and (ACA)-(MA)PbI4 (IPA = isopropylammonium, MA = methylammonium, ACA = acetamidinium). These compounds are prepared from mixing small organic cations, where they crystallize in a Ruddlesden-Popper type structure and a structure with alternating cations in the interlayer space, respectively. The crystal structures are compared in detail with related structures, and electronic structures are analyzed using density functional theory based calculations. Time-resolved microwave conductivity measurements are employed to provide insight into charge transport in these compounds. This work exemplifies the unusual templating role of small organic cations in the layered halide compounds.