Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

Abstract

Two‐dimensional (2D) hybrid perovskites have shown many attractive properties associated with their soft lattices and multiple quantum well structure. Herein, we report the synthesis and characterization of two new multifunctional 2D hybrid perovskites, (PED)CuCl4 and (BED)2CuCl6, which show reversible thermochromic behavior, dramatic temperature‐dependent conductivity change, and strong ferromagnetism. Upon temperature change, the (PED)CuCl4 and (BED)2CuCl6 crystals exhibit a reversible color change between yellow and red‐brown. The associated structural changes were monitored by in situ temperature‐dependent powder X‐ray diffraction (PXRD). The (BED)2CuCl6 exhibits superior thermal stability, with a thermochromic working temperature up to 443 K. The conductivity of (BED)2CuCl6 changes over six orders of magnitude upon temperature change. The 2D perovskites exhibit ferromagnetic properties with Curie temperatures around 13 K.

Single crystal of two-dimensional mixed-halide copper-based perovskites with reversible thermochromism

“…As a result, copper-based perovskites form a 2D layered structure with formula A 2 CuX 4 , where X is a halogen and A is the alkyl ammonium cation located as spacers between the (2D) [CuX 4 ] 2À layers. Two-dimensional Cu-based perovskites have been previously studied as promising candidates for lead-free perovskite photovoltaics, 15,16 Li + ion batteries, 19 and Heisenberg ferromagnets, [24][25][26] and exhibit thermochromic behaviors 17,18 and magnetic properties. [20][21][22][23] Mixed halides in a 2D copper-based hybrid perovskite, (CH 3 NH 3 ) 2 CuCl x Br 4Àx , play a crucial role in tuning properties beyond those of pure halide perovskites.…”

A Chiral Thermochromic Ferroelastic with Seven Physical Channel Switches

“…Therefore, the thermochromic effect is attributed to the red‐shift of electronic absorption bands with increase in temperature. From a microscopic point of view, the deformation of CuCl 4 anions through phase transition may be the root cause for the thermochromism . The inherent changes in the absorption window could become a strong support for future specific signal processing by using spectral encryption and signal detection.…”

Mixed Group 14–15 Metalates as Model Compounds for Doped Lead Halide Perovskites

“…Herein, we present the organic–inorganic 14–15 halogenido metalates (BED) 4 PbE 2 I 16 (BED= N ‐benzylethylenediammonium; E=Sb ( 1 ), Bi ( 2 )). Inspired by recent work on cuprates using BED, [41] we aimed to produce layered group 14–15 perovskites, similar to examples introduced by Solis‐Ibarra [42–44] . Somewhat puzzling, mixed 14–15 halogenido metalates have been restricted to the stabilization of polycationic clusters, as shown by Ruck [45–48] .…”