Expanding The Diversity of Intra-Layer Coupling Interactions in Mosaic Alloys of Layered Halide Perovskites

A wide range of physical properties associated with layered (two-dimensional) perovskites have been realized owing to, among other factors, the vast composition space of the inorganic layer and molecular diversity in organoammonium cations. A new class of layered halide perovskites recently discovered by our group, termed “mosaic” perovskites, form through alloying of single and double layered perovskites and demonstrate incorporation of three distinct metal ions. The first example of these disordered alloys comprised Cu(I), Cu(II), and In(III) ions in the perovskite layer, leading to emergent optoelectronic properties explained by intervalence charge transfer between Cu ions.<br/><br/>Here, we expand the diversity of mosaic layered perovskite alloys through exploration of transition-metal ion pairs that engender strong intra-layer coupling. We demonstrate that features of the known Cu(I)-Cu(II)-In(III) mosaic alloy, including the proposed role of the Cu(II) Jahn-Teller distortion, can be used to systematically evaluate candidate alloys and experimentally realize new examples of mosaic alloys. Facile synthetic methods to produce these novel alloys will also be discussed. Overall, these mosaic halide-perovskite alloys represent a platform for rational design of intra-layer coupling interactions within layered halides beyond the conventional compositional limitations of single or double perovskites. We discuss approaches to exploit such interactions alongside our perspective on the interplay between stability and disorder in these complex mixtures.