Windows

Abstract

The term Smart Window was introduced in the mid 1980s to describe optically switchable electrochromic glazings. These devices exemplify the fundamental characteristic of all “smart windows”: controllable variation in the optical transmittance of the window. The variation in optical transmittance of electrochromic smart windows occurs through the simultaneous injection of electrons and ions into an electrochromic material. This leads to the development of either a broad absorption band or a reflection edge (depending on the details of the material preparation) that leads to a low transmittance state. The process is reversible; extraction of the ions and electrons returns the material to a transparent state. The control of the process is accomplished by applying a small voltage (or passing a small current) that controls ion injection and extraction. Since the initial discovery of electrochromism in thin film WO 3 in 1969, an enormous amount of research has been directed toward the goal of large area switchable windows for architectural applications. This initially focused on electrochromic systems that covered a wide range of materials and device structures. During the 1980s and subsequently, several alternate optical switching systems were developed that fall into the general category of smart windows. These include other electrically activated systems such as suspended particle devices and phase dispersed liquid crystals temperature controlled switchable devices such as thermochromic and thermotropic devices, and recently developed gasochromic devices that are controlled by using reducing or oxidizing gas mixtures in a window unit.

In Situ Precipitation of Gold Nanoparticles onto Glass for Potential Architectural Applications

“…Pyrolytic coatings are durable, however the disadvantage of the process is the requirement that it can only be applied at the time of manufacture of the glass. Another scheme is to deposit partially reflective films of Au, Ag, TiN, ZrN, Cr x N, Si 3 N 4 , SnO 2 or In 2 O 3 onto glass by vacuum sputtering 1,5 . In this case the glass is at ambient temperature during the process.…”

“…These films are usually sandwiched between layers of transparent dielectrics of high refractive index, such as ZnO, Nb 2 O 5 , Bi 2 0 3 , or TiO 2 . 5,6 The industrial-scale production of large areas of such coated glasses, using magnetron sputtering, began in the early 1980s and is growing steadily. 7 Unfortunately, the high cost of applying these coatings (e.g.…”

Potentiostatic Reversible Photoelectrochromism: An Effect Appearing in Nanoporous TiO2/Ni(OH)2 Thin Films

“…This class of materials alters significantly and in a controlled fashion the light reflection or transmission due to a reversible coloration and bleaching induced by the application of an external potential. These promising characteristics have already led to the commercialization of electrochromic devices offering controllable light reflection or transmission in nonreflective mirrors − /nonemissive displays , or in windows. − The most successful current application of these materials is in nonreflective automotive rear-view mirrors. However, the most widely discussed potential application of electrochromic materials is in the fabrication of the so-called “smart windows”, which can regulate the transmission of the incoming light due to a bias-induced color change of the material.…”