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.