Recent advances in VO₂-based thermochromic composites for smart windows

Abstract

Vanadium dioxide (VO2) is a well-known thermochromic material since it exhibits a notable optical variation in the near-infrared region from transmitting to reflecting upon the semiconductor-to-metal phase transition (SMT).

Vanadium dioxide based Fabry-Perot emitter for dynamic radiative cooling applications

“…One such material is vanadium dioxide (VO2), which exhibits an insulator-to-metal transition and a dramatic change in infrared optical properties near a temperature of 68 ºC [11]. VO2 nanoparticles and thin films have been extensively studied for smart window applications, where the objective is to modulate the near-infrared solar transmittance while providing high visible transparency [12][13][14][15]. For instance, Powell et al [16] recently fabricated VO2/SiO2/TiO2 multilayers for energy saving windows and achieved a 15.29% solar modulation from the insulating VO2 to the metallic VO2 state.…”

Recent Advances in Hybrid Optical Materials: Integrating Nanoparticles within a Glass Matrix

“…To functionalize glass window with thermochromic properties, a layer of thermoresponsive materials that can reversibly alter their optical properties such as reflectance, emittance, or transmittance at different thermal stimulus levels is required. Vanadium dioxide (VO 2 ) has been the most popular thermoresponsive material (for thermochromic properties) for decades and remains so far . The thermoresponsive characteristic of VO 2 stems from its reversible phase switching behavior commonly known as metal–insulator transition (MIT), at a critical temperature ( T c ) around 68 °C 116c.…”

“…Vanadium dioxide (VO 2 ) has been the most popular thermoresponsive material (for thermochromic properties) for decades and remains so far . The thermoresponsive characteristic of VO 2 stems from its reversible phase switching behavior commonly known as metal–insulator transition (MIT), at a critical temperature ( T c ) around 68 °C 116c. This first‐order phase transition of VO 2 is accompanied by a dramatic modification of the optical absorbance; below T c , VO 2 is in its semiconductor state (monoclinic) for which infrared light transmits, whereas at the increased temperature ( T > T c ) metallic phase of VO 2 (tetragonal) is transferred and infrared light is blocked.…”

“…In addition to T c , the thermoresponsive performance of VO 2 is characterized by two transmittance related parameters: the luminous transmittance ( T lum ) and solar transmittance modulation (Δ T sol ). T lum is the integral of the transmittance of the thermochromic window across the vis spectrum (0.4 < λ < 0.7 µm); Δ T sol is the difference between the integral of the transmittance of the thermochromic window over the entire solar spectrum (0.2 < λ < 3 µm) for the two respective phases of VO 2 . For building architecture applications, the ideal VO 2 ‐based thermoresponsive layer has a T c near room temperature (20–25 °C), T lum > 60% and Δ T sol > 10% …”

“…The general strategy of decreasing T c is via doping transition metal ions into VO 2 . The most extensively studied dopant is W 6+ , which leads to T c of around 29 °C 116a,118. However, doping induces absorbance in the visible.…”