A new class of organic–inorganic single and double hybrid perovskites with a diammonium-halide-diammonium spacer layer

Abstract

Hybrid organic–inorganic perovskites (HOIPs) can be molecularly engineered to exhibit diverse functionalities such as chirality, ferroelectricity and photovoltaics. To date, research on layered HOIPs has mostly focused on Ruddlesden–Popper (RP) or Dion–Jacobson (DJ) type structural motifs. From the viewpoint of synthetic chemistry, it is interesting to explore structural motifs beyond these well-studied classes using rational synthetic routes. Here we report the synthesis of a new family of layered HOIPs named diammonium-halide-diammonium (DHD) perovskites. A DHD perovskite is distinguished by its organic ‘spacer’ layer consisting of diammonium-halide-diammonium. Based on the DHD perovskite family, we have successfully synthesized the elusive iodide-based lead-free double perovskite systems. We present the key chemical and structural design considerations for Cu⁺/Bi³⁺ and Ag⁺/Bi³⁺ DHD double perovskite systems, using 3-aminopyrrolidinium (3AP) and ethylenediammonium (ED) as the organic A-site cation. Finally, ferroelectricity can be achieved by introducing chiral 3-aminopyrroline cations into the crystal structure, which demonstrates the structure flexibility and potential applications of this new class of perovskites.