Electrochromic materials and devices for energy efficiency and human comfort in buildings: A critical review

Abstract

Electrochromic (EC) materials can be integrated in thin-film devices and used for modulating optical transmittance. The technology has recently been implemented in large-area glazing (windows and glass facades) in order to create buildings which combine energy efficiency with good indoor comfort. This critical review describes the basics of EC technology, provides a case study related to EC foils for glass lamination, and discusses a number of future aspects. Ample literature references are given with the object of providing an easy entrance to the burgeoning research field of electrochromics.

Electrochromic Effect in Titanium Carbide MXene Thin Films Produced by Dip‐Coating

“…The parameters studied during optimization of the technique were: MXene concentration (1-10 mg mL −1 ), number of dips (1)(2)(3)(4)(5) and MXene flake size. Then, a plasma treatment (Tergeo Plus, Pie Scientific) at 50 W with a mixture of O 2 and Ar (3 and 5 sccm) for 5 min was applied to the substrates for further cleaning and to improve their hydrophilicity.…”

“…However, when an anodic potential outside the voltage window (0.1 V/Ag) was applied, an irreversible increase of transmittance was observed (inset Figure 2c), indicative of the irreversible oxidation of Ti 3 C 2 T x . [5] In Figure 3, the smooth and immediate switching rate of the Ti 3 C 2 T x electrochromic device (device configuration in Figure 1a,b) at different potentials from 0.0 to −1.0 V/Ag was displayed using 1 m H 3 PO 4 aqueous electrolyte (instead of H 3 PO 4 /PVA gel electrolyte, to avoid any possible diffusion limitation of the gel). [5] In Figure 3, the smooth and immediate switching rate of the Ti 3 C 2 T x electrochromic device (device configuration in Figure 1a,b) at different potentials from 0.0 to −1.0 V/Ag was displayed using 1 m H 3 PO 4 aqueous electrolyte (instead of H 3 PO 4 /PVA gel electrolyte, to avoid any possible diffusion limitation of the gel).…”

“…[2,3] An electrochromic device generally consists of a transparent conductive electrode (TCE), active electrochromic film, ion conductor, and ion storage film. [5] The most common TCE material is indium tin oxide (ITO) due to its low resistivity (<150 µΩ cm) and high transparency (T > 90%) in the visible range. [6,7] However, indium resources are limited and the material is expensive.…”

New Roll‐to‐Roll Processable PEDOT‐Based Polymer with Colorless Bleached State for Flexible Electrochromic Devices

“…Conjugated polymers are one of the main classes of materials that exhibit EC properties as thin films. [3,6,11,[18][19][20][21][22][23] A drawback of most ECPs is the lack of a highly transmissive and fully colorless bleached state. ECPs, therefore, are a large-scale and low-cost solution for ECDs since they can be coated on flexible plastic substrates by means of wet chemical approaches.…”

“…[12][13][14][15][16][17] Furthermore, ECPs feature a wide range of vivid colors, response times in the range of seconds, and light transmittance change over 60%. [3,6,7,[27][28][29][30][31][32][33][34] Other materials, such as multichromophoric polymers, can actually offer suitable bleached and colored states, but require elaborate synthesis routes and have an electrochemical operating window, which poses serious stability problems. The bandgap between the highest occupied π-electron band and the lowest unoccupied band determines the EC properties like color and color change.…”