Nanostructured inorganic electrochromic materials for light applications

Abstract

Electrochromism, an emerging energy conversion technology, has attracted immense interest due to its various applications including bistable displays, optical filters, variable optical attenuators, optical switches, and energy-efficient smart windows. Currently, the major drawback for the development of electrochromism is the slow switching speed, especially in inorganic electrochromic materials. The slow switching speed is mainly attributed to slow reaction kinetics of the dense inorganic electrochromic films. As such, an efficient design of nanostructured electrochromic materials is a key strategy to attain a rapid switching speed for their real-world applications. In this review article, we summarize the classifications of electrochromic materials, including inorganic materials (e.g., transition metal oxides, Prussian blue, and polyoxometalates), organic materials (e.g., polymers, covalent organic frameworks, and viologens), inorganic-organic hybrids, and plasmonic materials. We also discuss the electrochromic properties and synthesis methods for various nanostructured inorganic electrochromic materials depending on structure/morphology engineering, doping techniques, and crystal phase design. Finally, we outline the major challenges to be solved and discuss the outlooks and our perspectives for the development of high-performance nanostructured electrochromic materials.

Electrochromic Inorganic Nanostructures with High Chromaticity and Superior Brightness

“… 16 Furthermore, WO 3 has proven stable enough for use in commercial devices such as smart windows. 4 …”

“…The two most fundamental properties for good image quality are brightness (which translates to reflectance for electronic paper) and chromaticity (the color purity measured as the gamut in the CIE). 5 Although many innovative and promising nanoscale designs have been presented recently, 4 the colors may be limited to the green-red spectral region 11 and/or the reflectance is low. 10 In fact, the aspect of brightness is often neglected: if absolute reflectance values are presented at all, it is not explained properly how they were measured.…”

Advances in Energy‐Efficient Plasmonic Electrochromic Smart Windows Based on Metal Oxide Nanocrystals

“…Different from the traditional electrochromism triggered by the electrochemical Faraday redox reaction, doped metal oxide NCs deliver a new electrochemical capacitance plasmonic EC mechanism. The nanostructure of the films and the utilized electrolyte systems are the main factors that significantly affect the EC properties of traditional EC materials, [78][79][80] whereas the crystal size, morphology, and specific surface area of metal oxide plasmonic NCs have a great influence on their EC properties. This new electrochemical capacitance plasmonic EC effect, which dynamically adjusts the absorption of LSPR by injecting and extracting electrons through electrochemical capacitor charging, can selectively adjust the transmittance of the NIR light from solar irradiation.…”

“…In addition, response times and coloration efficiency are important parameters to evaluate the performance of PESWs. [79] Response times contain a coloration time (τ c ) and a bleaching time (τ b ), which usually refers to the time required for a 90% change of optical modulation in the bleached/colored state. [79] The coloration efficiency is defined as follows [77,83] Reproduced with permission.…”

“…[79] Response times contain a coloration time (τ c ) and a bleaching time (τ b ), which usually refers to the time required for a 90% change of optical modulation in the bleached/colored state. [79] The coloration efficiency is defined as follows [77,83] Reproduced with permission. [77] Copyright 2013, The Royal Society of Chemistry.…”