Thermochromic Coatings for Intelligent Architectural Glazing

Abstract

Abstract. Thermochromic glazing is a type of intelligent glazing; one where the properties of the glazing change according to some external stimulus. More particularly a thermochromic window is a device that changes its transmission and reflectance properties at a critical temperature (T c ). At this specific temperature the material undergoes a semi-conductor to metal transition. At temperatures lower than T c the window lets all of the solar energy that hits it through. At temperatures above T c the window reflects the infra-red portion of solar energy. In such a way thermochromic windows may help reduce air conditioning and heating costs leading to more energy efficient buildings. This review details the nature of the semi-conductor to metal transition and indicates how substitutional doping within a crystal lattice can be used to manipulate and fine tune the critical temperature. Also detailed is the underlying science and methodologies so far employed in the production of thermochromic thin films.

Thermochromic undoped and Mg-doped VO2 thin films and nanoparticles: Optical properties and performance limits for energy efficient windows

“…Below this temperature, at τ < τ c , VO 2 is semiconducting and infrared transmitting, whereas it is metallic and infrared reflecting at τ > τ c . As τ c is rather close to room temperature, VO 2 -based materials are of interest for applications on energy efficient windows, [12][13][14][15][16][17][18][19] specifically for passively modulating the solar energy throughput depending on temperature. The potential energy saving can be high, especially in warm climates.…”

The Effect of Transition Hysteresis Width in Thermochromic Glazing Systems

“…It is not well understood how to obtain low hysteresis widths, although uniform particle size has been suggested as one possible route [12]. In any case, the vast majority of samples in the literature have widths of 5˚C -10 ˚C [16,17,[26][27][28][29][30]. Which gives a comparable or moderately enhanced performance when compared to the absorbing glass, and a significantly improved performance over the sputtered silver glass.…”

“…The transition tempera-ture has also been shown to be affected by film strain [11] and it has been demonstrated that strain can be introduced by careful choice of deposition conditions [12]. Tungsten doped vanadium dioxide films have been prepared by a variety of methods including physical vapour deposition [13], sol-gel [14], and chemical vapour deposition (CVD) methodologies [15][16][17]. CVD routes to the production of VO 2 films are generally considered more attractive because of the ability to integrate CVD processes with high volume float glass manufacture and the physical properties of CVD produced films, which are generally adherent and durable [18].…”

Thermochromic Thin Films and Nanocomposites for Smart Glazing

“…The transition temperature has also been shown to be affected by film strain [64] and it has been demonstrated that strain can be introduced by careful choice of deposition conditions [65]. Tungsten doped vanadium dioxide films have been prepared by a variety of methods including sol-gel [66], sputtering [67], and chemical vapour deposition (CVD) methodologies [68][69][70]. CVD routes to the production of doped V0 2 films are generally considered more attractive because of the compatibility of CVD processes with high volume glass manufacture and the physical properties of CVD produced films which are usually adherent and long lasting.…”