Perovskite-Coated Thermochromic Transparent Wood: A Novel Material for Smart Windows in Energy-Efficient and Sustainable Buildings

Transparent wood (TW) has emerged as a sustainable alternative to conventional glass as an energy-efficient window glazing material owing to its exceptional optical transparency and superior mechanical and thermal performances. However, it is challenging to develop the TW-based color-switching smart windows with both high optical performance and mechanical strengths. In this work, an optically switchable and mechanically robust perovskite-coated thermochromic transparent wood (PTTW) is developed for use as smart windows to achieve an effective solar modulation and thermal management. PTTW exhibits a substantial solar modulation ability Δτ sol of 21.6% and a high clear-state luminous transmittance τ lum of 78.0%, which enable an efficient thermal regulation while ensuring high visual clarity. PTTW also offers enhanced mechanical properties (i.e., tensile strength σ tens = 71.4 MPa and flexural strength σ flex = 93.1 MPa) and improved thermal properties [i.e., thermal conductivity K = 0.247 W/(m·K) and heat capacity C = 1.69 J/(g·°C)] compared to glass-based smart windows, as well as excellent performance stability (i.e., 200 heating–cooling cycles), manifesting its applicability in real building scenarios. In addition, PTTW also demonstrates a remarkable thermal-regulating performance (i.e., 5.44 °C indoor air temperature regulation) and an energy-saving potential (i.e., 12.9% heating, ventilation, and air conditioning energy savings) in Hong Kong. Overall, this study contributes to the progression toward energy-efficient and sustainable buildings.