Thermochromic Materials for Smart Windows: A State-of-Art Review

Abstract

Smart windows that regulate solar energy by changing optical characteristics have recently gained tremendous interest for energy-saving and indoor-comfort applications. Among them, thermochromic smart windows are promising because of their simplicity for industrial production and ease of implementation. Although significant advancements have been reported on thermochromic materials, both optical and transition properties remain unsatisfactory. This review focuses on the recent advancement of thermochromic materials for smart windows in terms of operation, performance, and potential for commercialization. It discusses the parameters typically used for gauging performance and provides a summary and comparison of various promising thermochromic materials, including vanadium dioxide, hydrogels, and perovskites. The article also points the challenges in the practical implementation of these materials and provides an outlook for future development.

Thermochromic hydrogels with an adjustable critical response temperature for temperature monitoring and smart windows

“…Phase change materials are classic smart window substrates that have been widely studied for thermochromic smart windows, such as vanadium oxide (VO 2 , T k E 68 1C), hydroxypropyl cellulose (HPC, T k E 50 1C), and poly (N-isopropyl acrylamide) (PNIPAM, T k E 32.5 1C) etc. 10,[13][14][15][16] When the ambient temperature reaches the T k , these materials can achieve a reversible ''transparent-opaque'' transition. However, the T k of most conventional thermochromic materials is higher than the comfortable temperature of the human body, and it is difficult to freely adjust.…”

Review on Mechanoresponsive Smart Windows: Structures and Driving Modes

“…The optical properties are tunable due to the characteristic of redox reaction or ion embedding/detachment under electric field [ 10 ]. The thermochromic materials can change the colors with the temperature due to the thermal decomposition or geometrical conformation change [ 11 ]. When exposed to specific wavelengths of light, photochromic materials can change color resulting from the chemical bond homolytic reaction or pericyclic reaction [ 12 ].…”

An optimal climate-adaptable hydrogel-filled smart window for the energy-saving built environment

“…Hydrogels can exhibit reversible hydrophilic/hydrophobic phase transitions around the lower critical solution temperature (LCST). [8][9][10] Simultaneous thermochromism and cool/warm tone switchability functions of hydrogels can be beneficial for smart windows.…”