Precise Design of VO₂Thin Films for Smart Windows by Employing Thickness‐Dependent Refractive Index

Abstract

Vanadium dioxide (VO2) is an adjustable refractive index material and has capability of behaving as semiconductor or conductor depending on its temperature. Such a condition makes it as a material which can be employed in fabricating thermochromic smart windows. The transmission characteristics of these type of windows strongly depend on the thickness of the film. Therefore, some calculations are required to optimize the VO2 thickness. Since the refractive index of VO2 thin film is thickness dependent, therefore, in calculating the transmission of light spectrum from VO2 thin films, a unique refractive index cannot be utilized. Herein, using three theoretical models (Lorentz–Drude oscillator, Lorentz oscillator, and Tauc–Lorentz) and employing experimental results from previous reports, a collection of thickness‐dependent refractive indexes of VO2 films is provided. More precise transmission can be achieved using this set of refractive index data in the calculations which agree with those of experiments. These results also make capable to determine optimized film thickness for any desired transmission performance. This method is useful for design of VO2‐based thermochromic smart windows.

Plasmonic switches based on VO2 as the phase change material

“…However, because the focus of this review paper is only plasmonic switching, we will focus only on the change in optical properties that VO 2 undergoes due to the underlying changes in the refractive index. The optical constants of VO 2 can be described by using the classical dispersion model [132][133][134] which is based on the sum of the Lorentz and Drude oscillators as follows:…”