Switchable Dielectric Two-Dimensional Lead-Free Perovskite with Reversible Thermochromic Response

Two-dimensional (2D) organic–inorganic hybrid perovskites (OIHPs) have attracted great interest due to their unique properties for optical, thermal, electric, force, and magnetic applications. However, although some 2D HOIPs with thermochromic properties have been obtained, the issue of toxicity of lead and single-stimulus response impose restrictions on their further applications. To overcome this limitation, we scientifically design and fabricate a novel two-dimensional organic–inorganic hybrid lead-free perovskite [2,5-DCA]2·[CuCl4] (1), which simultaneously possesses excellent reversible chromic/dielectric response under thermal stimulation. Specifically, along with the change in temperature (303–413 K), crystal 1 displays a reversible color change between yellow-green and red-brown with a band gap variation from 2.25 to 2.05 eV. Besides, compared with other thermochromic perovskites, crystal 1 also exhibits a sensitive dielectric transition at a lower phase-transition point (around 369 K) with high fatigue resistance. This study demonstrates a reliable strategy for the fabrication of multiple-stimuli-responsive materials and sheds light on the study of two-dimensional lead-free perovskites in smart windows.