A combined experimental and theoretical study into the performance of multilayer vanadium dioxide nanocomposites for energy saving applications

In the built environment there is an increasing issue of heat management, with buildings expending significant energy resources to maintain comfortable living temperatures. In many parts of the world, this entails the use of both heating and cooling during daylight hours depending on ambient temperatures. Due to the variation in the desired temperature control classical solutions can become counter productive in their aim of maintaining comfortable temperatures, therefore it is important to employ adaptive solutions that vary their functionality based on circumstance, such as window films with thermochromic or electrochromic properties. Here, we present a design for a thermochromic smart window film based on a multilayer stack of silica, titania and vanadium dioxide (VO 2 ). The design makes use of coherent interference within the multi-layered structure to suppress the typically high reflection of visible light and improve the reflective component of solar modulation. This allows us to simultaneously improve the visible transmittance and solar modulation of the film above what would be possible with a single layer of vanadium dioxide film. Guided by simulation, the multilayer structure is fabricated using a scalable sol-gel method and results are compared with simulations and a single layer VO 2 reference sample.