Researchers from City University of Hong Kong have introduced a novel and durable 2D thermochromic perovskite, Tha2MAPbI4 (TMPI, Tha = thiourea, MA = methylamine), wherein Tha acts as a Lewis acid-base adduct. TMPI demonstrates a reversible transition, achieving 83.7% luminous transmittance in the cold state and 35.2% in the hot state, thereby showcasing a substantial solar modulation ability of 24.7%.
The background for this development is that despite growing interest in thermochromic metal halide perovskite (MHPs) for smart window applications, existing MHP smart windows predominantly feature 3D perovskite, which exhibits a deficiency in environmental stability, presenting persistent challenges for practical applications.
Further analysis of the crystal structure reveals that the thermochromic behavior of TMPI arises from a phase transition between 0D perovskite and 2D perovskite, induced by a dehydration-hydration process.
Notably, TMPI maintains thermochromic properties even after direct exposure to 75% relative humidity and 25 °C air for up to 28 days, a stark contrast to traditional 3D perovskites that lose their thermochromic capabilities within a few days under similar conditions.
This research unveils TMPI as a thermochromic 2D perovskite that marks a significant advancement in environmental stability, indicating promising prospects for thermochromic smart windows.
