Pt/VO2 double-layered films combining thermochromic properties with low emissivity

This study involves the optical properties of Pt/VO2 composite films, with a Pt top layer and a VO2 bottom layer. VO2 and Pt films were grown on fused silica substrates by polymer-assisted deposition and sputtering, respectively. These Pt/VO2 films were characterized by scanning electron microscopy, UV–visible–NIR spectrophotometry, Fourier transform infrared spectrometry, four-point probe and Raman spectroscopy. The results indicate that these Pt/VO2 films can enhance the infrared reflectivity while retaining their thermochromic properties. Although the visible transmittance is depressed by these Pt layers, the addition of antireflection coatings boosts the transmittance from 25.1% to 37.9% at 0.55 μm. In addition, the semiconductor-metal (S-M) transition temperatures of Pt/VO2 films shift to lower temperatures in the heating semicycle (Tc,h), from 67.8 °C for a pure VO2 film to 58.5 °C for a VO2 film covered with a 9 nm Pt layer. This work provides an important prototype structure for the development of new smart windows that combine thermochromic properties with low emissivity.