Coloration of tungsten oxide electrochromic thin films at high bias potentials and low intercalation levels

Rojas-González, Edgar A.; Niklasson, Gunnar A.

doi:10.1016/j.mlblux.2020.100048

Cited by 2 publications

(3 citation statements)

References 13 publications

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“…In order to resolve the contributions from these elements not only should inductive effects be suppressed but also measurements be performed at higher potentials where the contribution from the adsorption process becomes smaller. This was possible in EIS measurements on an aWO 3 WE performed in our previous work 59 (using the same electrolyte and deposition conditions as those employed here) at potentials between 2:8 and 3:7 V vs Li=Li þ . The question, therefore, arises whether effects of ZCPEdl (ω) and R ct might be significant for the present data at 3:15 V. In the previous measurements, 59 R ct exhibited values of about 14 and 3 Ω at bias potentials of 3:2 and 3:1 V vs Li=Li þ , respectively.…”

Section: Discussionmentioning

confidence: 96%

“…This was possible in EIS measurements on an aWO 3 WE performed in our previous work 59 (using the same electrolyte and deposition conditions as those employed here) at potentials between 2:8 and 3:7 V vs Li=Li þ . The question, therefore, arises whether effects of ZCPEdl (ω) and R ct might be significant for the present data at 3:15 V. In the previous measurements, 59 R ct exhibited values of about 14 and 3 Ω at bias potentials of 3:2 and 3:1 V vs Li=Li þ , respectively. In these cases, the respective values of f dl were of about 536 and 4106 Hz-much higher than the upper frequency limits of the complex optical capacitance spectra shown here (about 10 Hz).…”

Section: Discussionmentioning

confidence: 96%

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Charge coloration dynamics of electrochromic amorphous tungsten oxide studied by simultaneous electrochemical and color impedance measurements

Rojas-González

Niklasson

2021

Journal of Applied Physics

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The coloration mechanisms in electrochromic systems can be probed by comparing the dynamics of the electrical and optical responses. In this paper, the linear frequency-dependent electrical and optical responses of an amorphous tungsten oxide thin film were measured simultaneously by a combination of two techniques-that is, electrochemical impedance spectroscopy (EIS) and the so-called color impedance spectroscopy. This was done at different bias potentials and their associated intercalation levels. Equivalent circuit fitting to the EIS spectra was used to extract the Faradaic components from the total impedance response. The latter were assigned to an intermediate adsorption step before the intercalation and to the diffusion of the electron-ion couple in the film. A quantity denoted complex optical capacitance was compared to the complex electrical capacitance-particularly, their expressions are related to the Faradaic processes. The coloration at low intercalation levels followed both the adsorption and diffusion phenomena. Conversely, the diffusion contribution was dominant at high intercalation levels and the adsorption one seemed to be negligible in this case. The complex spectra of perfectly synchronized electrical and optical responses are expected to differ only by a multiplying factor. This was the case at low intercalation levels, apart from small deviations at high frequencies. A clear departure from this behavior was observed as the intercalation level increased. A combination of frequency-dependent techniques, as presented here, can help to elucidate the dynamics of the coloration mechanisms in electrochromic materials at various conditions-for example, at different intercalation levels and optical wavelengths.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 96%

Charge coloration dynamics of electrochromic amorphous tungsten oxide studied by simultaneous electrochemical and color impedance measurements

Rojas-González

Niklasson

2021

Journal of Applied Physics

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“…Nowadays, the importance of WO 3 films has grown [ 79 , 80 ] due to their use in “Smart Windows”, which smartly regulate indoor solar radiation by changing their optical transmittance, contributing to a significant reduction in a building’s energy consumption (as a result of the optimization of air conditioning consumption) and helping to create comfortable indoor environments [ 81 ]. However, despite all the advantages of WO 3 films, their life cycle is not very long: continuous switching between colored and colorless states causes irreversible structural changes that affect their optical and electrical properties, ultimately leading to material degradation, the so-called “aging” effect [ 82 ].…”

Section: Electrochromism and Electrochromic Materials: Classification And Applicationsmentioning

confidence: 99%

A Brief Overview of Electrochromic Materials and Related Devices: A Nanostructured Materials Perspective

et al. 2021

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Exactly 50 years ago, the first article on electrochromism was published. Today electrochromic materials are highly popular in various devices. Interest in nanostructured electrochromic and nanocomposite organic/inorganic nanostructured electrochromic materials has increased in the last decade. These materials can enhance the electrochemical and electrochromic properties of devices related to them. This article describes electrochromic materials, proposes their classification and systematization for organic inorganic and nanostructured electrochromic materials, identifies their advantages and shortcomings, analyzes current tendencies in the development of nanomaterials used in electrochromic coatings (films) and their practical use in various optical devices for protection from light radiation, in particular, their use as light filters and light modulators for optoelectronic devices, as well as methods for their preparation. The modern technologies of “Smart Windows”, which are based on chromogenic materials and liquid crystals, are analyzed, and their advantages and disadvantages are also given. Various types of chromogenic materials are presented, examples of which include photochromic, thermochromic and gasochromic materials, as well as the main physical effects affecting changes in their optical properties. Additionally, this study describes electrochromic technologies based on WO3 films prepared by different methods, such as electrochemical deposition, magnetron sputtering, spray pyrolysis, sol–gel, etc. An example of an electrochromic “Smart Window” based on WO3 is shown in the article. A modern analysis of electrochromic devices based on nanostructured materials used in various applications is presented. The paper discusses the causes of internal and external size effects in the process of modifying WO3 electrochromic films using nanomaterials, in particular, GO/rGO nanomaterials.

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Coloration of tungsten oxide electrochromic thin films at high bias potentials and low intercalation levels

Cited by 2 publications

References 13 publications

Charge coloration dynamics of electrochromic amorphous tungsten oxide studied by simultaneous electrochemical and color impedance measurements

Charge coloration dynamics of electrochromic amorphous tungsten oxide studied by simultaneous electrochemical and color impedance measurements

A Brief Overview of Electrochromic Materials and Related Devices: A Nanostructured Materials Perspective

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