Robust and Swiftly Reversible Thermochromic Behavior of a 2D Perovskite of (CH(CHNH))(CHNH)[PbI] for Smart Window and Photovoltaic Smart Window Applications.

Highly robust, swiftly reversible thermochromic nature of a two-dimensional (2D) perovskite of (PDMA)(CHNH)PbI, nominally prepared as = 2 is found, where PDMA = CH(CHNH). A wide band gap variation from 700 to 430 nm is observed between room temperature and >60 °C under ambient conditions, resulting from moisture absorption and desorption. X-ray diffraction and Fourier-transform infrared spectroscopy are performed to analyze the hydrated and dehydrated states. Furthermore, the (PDMA)(CHNH)PbI film is demonstrated as an active material for smart windows and thermochromic solar cells, which could lower the inside air temperature in an enclosed space and supply a power conversion efficiency of more than 0.5% at a high ambient temperature, respectively. Overall, we may pave a pathway for exploring the novel phenomena and applications of Dion-Jacobson 2D perovskites.