Effect of Structure of TiO2/Ag/TiO2 Composite Films on Their Chromaticity

In order to obtain low energy consumption and comfortable color for human eyes, TiO2/Ag/TiO2 composite films of high reflectance in infrared wavelength range and desired color in visible range were prepared. The TiO2/Ag/TiO2 composite films can help minimize radiative heat exchange between the indoor and outdoor environments, thus saving energy for all-year cooling and heating while satisfying the required aesthetical effect. The effects of the thickness and layers of Ag and TiO2 films on the transmission, chromaticity and color difference were simulated by TFCalc. The results showed that as for the single structure TiO2/Ag/TiO2 film, the wavelength corresponding to maximum transmission did not change obviously, and the brightness decreased accordingly. The color saturation increased with the increase of the thickness of the Ag film simultaneously. However, the maximum transmittance changed little and the wavelength corresponding to maximum transmittance had red shift with the increase of TiO2 film thickness. Meanwhile, the brightness increased first and then decreased correspondingly, and the chromaticity changed from blue to yellow. Accordingly, the color deviation was more than 10 and less than 5 with changing the thickness of Ag and TiO2 films for 5 nm respectively. For the single-structure TiO2/Ag/TiO2, comfortable visual effect can be obtained by adopting the structure of 20 nm TiO2/15 nm Ag/20 nm TiO2 or 25 nm TiO2/20 nm Ag/ 25 nm TiO2. It was necessary to set the thickness of TiO2 films to negative deviation in order to achieve the purpose of low chromatic aberration. Compared with single-structure TiO2/Ag/TiO2 composite films, dual-structure TiO2/Ag/TiO2 films had shorter wavelength corresponding to maximum transmittance and narrower transmission band. It was interesting that the dual-structure TiO2/Ag/TiO2 film has higher maximum transmittance although it contained more layers of Ag films due to the coupling of surface plasmon polaritons of Ag films. Additionally, the chromatic aberration had a greater change with the thickness changing of Ag and TiO2 films. The chromatic aberration was more than 20 with thickness changing of Ag films for 5 nm. The chromaticity of dual-structure TiO2/Ag/TiO2 composite films varied from blue, sky blue, green, pink, yellow and orange. It was worth noting that more colour could be obtained by the dual-structure. Compatible stealth for visible light and near infrared can be achieved by adopting dual-structure of TiO2/Ag/TiO2 composite films which can enormously reduce the near infrared and form camouflage patterns to segment visible images. Finally, it is found that it could obtain high transmittance and comfortable colour of human eyes in visible region and low infrared reflectivity in infrared region and by adopting dual-structure of 25 nm TiO2/15 nm Ag/25 nm TiO2. In order to reduce the chromatic aberration of different batches of products. It is necessary to adopt negative and positive deviation respectively for Ag and TiO2 thickness in the industrial production. The TiO2/Ag/TiO2 composite film colour card is established. The colour of the composite films can be obtained by adopting different structures. The work provides insights for innovative energy-saving building envelope materials that can help achieve global carbon neutrality and sustainability. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.