Scalable Photochromic Film for Solar Heat and Daylight Management

Abstract The adaptive control of sunlight through photochromic smart windows could have a huge impact on the energy efficiency and daylight comfort in buildings. However, the fabrication of inorganic nanoparticle and polymer composite photochromic films with a high contrast ratio and high transparency/low haze remains a challenge. Here, a solution method is presented for the in situ growth of copper‐doped tungsten trioxide nanoparticles in polymethyl methacrylate, which allows a low‐cost preparation of photochromic films with a high luminous transparency (luminous transmittance T lum = 91%) and scalability (30 × 350 cm 2 ). High modulation of visible light (Δ T lum = 73%) and solar heat (modulation of solar transmittance Δ T sol = 73%, modulation of solar heat gain coefficient ΔSHGC = 0.5) of the film improves the indoor daylight comfort and energy efficiency. Simulation results show that low‐e windows with the photochromic film applied can greatly enhance the energy efficiency and daylight comfort. This photochromic film presents an attractive strategy for achieving more energy‐efficient buildings and carbon neutrality to combat global climate change.