Reversible phase transition and thermochromic response in hybrid copper-based perovskites

With the vigorous development of the photovoltaic hot topic, organic-inorganic hybrid perovskite (OIHP) has become the focus in the search for functional materials. Among them, layered 2D OIHPs provide the possibility of exfoliating the bulk material into thin nanosheets, which are essential building blocks for many electronic and optoelectronic devices. Herein, we successfully designed copper-based 2D hybrid perovskite (MBA)(2)CuCl4 (1) (MBA = 4-methoxybenzylaminum) and (BA)(2)CuCl4 (2) (BA = benzylaminium), and the former is reported for the first time. Among them, (MBA)(2)CuCl4 (1) exhibits a high phase transition temperature (430.25 K) with stable dielectric switching properties. Interestingly, both (MBA)(2)CuCl4 (1) and (BA)(2)CuCl4 (2) have reversible thermochromic responses, with a color change from yellow to dark brown between 300 and 390 K. The high phase transition temperature of 1 is remarkable compared to other copper-based thermochromic materials. Both compounds exhibit potential semiconductor properties. This study provides a new perspective for the design of phase transition materials with thermochromic responses and possess potential applications in smart windows.