Combatting climate change has gained significant global awareness resulting in a number of measures to reduce greenhouse gas emissions and even achieve net-zero carbon emissions. Currently buildings use large amounts of electricity through air conditioning, heating, and lighting. Additionally, significant energy is wasted due to heat loss and heat gain from windows.
For example, a building design may contain large windows to improve the aesthetics of the building, allow for outdoor viewing while indoors, and to provide natural light which reduces the need for indoor lighting. However, during cool periods, heat is lost from inside the building which requires heating the building and during warm periods, the poorly insulated glass causes overheating. When a building is overheated, either an air conditioning system is required or windows can be blocked with blinds or curtains. However, when the windows are blocked, natural light is reduced and indoor lighting is required.
Dynamic smart windows have been developed to variably adjust the color or opacity of the window through external stimuli to reduce heat loss and heat gain from windows. One smart window utilizes thermochromic based technologies which changes light transmittance based on temperature. For example, in cool temperatures, a cross-linked hydrophilic polymer chain will bond with surrounding water through hydrogen bonds resulting in high transmittance. In warmer temperatures, the hydrogen bonds are broken which scatters light and reduces the transmittance. While thermochromic materials are able to change transmittance, the materials lack user-control making the materials more appropriate for thermal radiation mitigation in spacecraft.
Another option is using photochromic devices which are adaptive based on light-based stimuli. For example, the material responds to incident solar radiation. When there is increased radiation, the window darkens and when there is decreased radiation, the window lightens. Photochromic devices work well in auto-dimming transition glasses, however, show problems when used in larger windows. More specifically, photochromic devices are activated by UV light. Therefore, if used in a window, the window would only dim when in direct sunlight and would not be able to dim in the case where the window is facing away from direct sunlight. Also, similarly to thermochromic based technologies, photochromic devices lack user-control.
Additionally, electrochromic devices are adaptive based on external electric potential. When a voltage is applied to these materials, ions from an electrode are attracted to a network within the semi-conductive structure. Ions can be inserted or extracted resulting in a reversible optical change. While some manufactures have been able to commercialize inorganic electrochromic smart windows (e.g., SageGlass, View, Inc. and Halio, Inc.), the uniform and scalable deposition is slow, expensive, and susceptible to defects that can cause shunting in the window. Also, the windows have poor color neutrality due to the materials commonly having a dark blue color. Even as some of these companies have improved the windows to reduce the previously mentioned issues, the price of these smart windows can be anywhere from $50 to $200 per square foot. Therefore, only commercial buildings in high income areas can afford such smart windows.
Accordingly, there is an on-going need for smart windows that are composed of materials that are UV stable, processable, and affordable. Additionally, smart windows should be able to last for a number of years and be durable. Lastly, the smart windows need to cover entire walls of buildings with tint uniformity, able to control heat flow while maintaining transparency, and allow user-control.
Disclosed embodiments relate to reversible metal electrodeposition materials with applications in dynamic smart windows. Embodiments simultaneously achieve high durability, color neutrality, low haze, fast switching speeds, and low-cost manufacturing. Additionally, the disclosed embodiments exhibit high contrast without the need for additional power to hold the material at a given optical state.
An exemplary method includes providing a reversible metal electrodeposition (RME) device that includes two transparent substrates, wherein each transparent substrate is on an outside of the device (e.g., a window), a working electrode located near one of the two transparent substrates, a counter electrode located near another of the two transparent substrates, an electrolyte solution located between the working electrode and the counter electrode. The method involves applying a pulsed voltage to the RME device, wherein the pulsed voltage includes an on phase and an off phase, so as to cause electrochemical deposition of metal ions from the electrolyte solution, creating a metallic film on the working electrode, reducing light transmittance, by the metallic film, through the RME device.
An exemplary reversible metal electrodeposition (RME) device includes two transparent substrates, wherein each transparent substrate is on an outside of the device, a working electrode located near one of the two transparent substrates, a counter electrode located near another of the two transparent substrates, and an electrolyte solution located between the working electrode and the counter electrode. A power source is also provided, which delivers a pulsed voltage to the working electrode and/or the counter electrode. During operation the RME device reversibly changes light transmittance through the device when the pulsed voltage is applied to the RME device which causes electrochemical deposition of metal ions from the electrolyte solution to create a metallic film on the working electrode.
In an embodiment the electrolyte solution includes water and at least one of Cu(ClO4), BiOClO4, HClO4, or LiClO4.
In an embodiment the working electrode is a transparent conducting oxide (TCO) working electrode.
In an embodiment the working electrode is a Pt modified ITO working electrode.
In an embodiment the metal ions include Cu and Bi.
In an embodiment the pulsed voltage has a duty cycle of about 5%, or about 10%, or about 15%, or about 20%, or about 25%, or about 50%, or about 60%, or from about 5% to about 60%, or any other range between two such values.
In an embodiment the pulsed voltage has a frequency of about 0.1 Hz, or about 0.5 Hz, or about 1 Hz, or about 5 Hz, or about 10 Hz, or about 15 Hz, or about 20 Hz, or from about 0.1 Hz to about 20 Hz, or any other range between two such values.
In an embodiment the reducing light transmittance (i.e., window tinting) results in about 0.1% transmittance, or about 1% transmittance, or about 5% transmittance, or about 10% transmittance, or about 15% transmittance or from about 0.1% transmittance to about 15% transmittance, or any other range between two such values.
In an embodiment the pulsed voltage is applied for about 0.1 second, or about 1 second, or about 10 seconds, or about 20 seconds, or about 30 seconds, or about 60 seconds, or about 120 seconds, or from about 0.1 second to about 120 seconds, or any other range between two such values.
In an embodiment the RME device is color neutral, with a chroma value of less than 10.
In an embodiment the user controls an amount of light transmittance reduction that is achieved.
In an embodiment the reduced light transmittance is reversible.
In an embodiment the the RME device is a window.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an indication of the scope of the claimed subject matter.
Various objects, features, characteristics, and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings and the appended claims, all of which form a part of this specification. In the Drawings, like reference numerals may be utilized to designate corresponding or similar parts in the various Figures, and the various elements depicted are not necessarily drawn to scale, wherein:
Disclosed embodiments relate to reversible metal electrodeposition materials with applications in dynamic smart windows using pulsed voltage electrodeposition. Embodiments simultaneously achieve high durability, color neutrality, low haze, fast switching speeds, and low-cost manufacturing. Additionally, the disclosed embodiments exhibit high contrast without the need for additional power to hold the material at a given optical state.
Disclosed embodiments are able to tint the window material to a 0.1% transmittance state faster initially than conventional plating methods. Additionally, disclosed embodiments reduce dendrite films in the material making disclosed embodiments more effective at blocking light. Also, disclosed embodiments result in compact, uniform, and smooth films that are more reflective and efficient at blocking light.
The dynamic smart window may be automatically controlled by stimuli or by a user to conform to the needs and preferences of the user. In some embodiments, the dynamic smart windows may be programmed to change based on day of the week and time of day. For example, in the case of an office building, the dynamic smart window may be in a full state 108 during the weekend when no employees are on site and may be in a clear state 102 when most employees arrive at work during the week.
In more detail, during the deposition phase 212, the metal ions in the electrolyte solution 206 are reduced due to the applied voltage creating the metal film 214 on the working electrode 204 causing the RME device to become opaque. In the dissolution phase 210, the metal ions in the metal film 214 are oxidized and dissolved back into the electrolyte solution 206 therefore removing the metal film 214 and causing the RME device to become transparent.
In some embodiments, the electrolyte solution 206 includes water, and one or more of Cu(ClO4), BiOClO4, HClO4, and/or LiClO4. In some embodiments, the working electrode 204 is an indium tin oxide (ITO) on a glass substrate which is modified to include platinum nano-particles to create a Pt modified ITO working electrode. In some embodiments, the metal ions that create the metal film 214 are copper (Cu) and/or bismuth (Bi) to maintain color neutrality of the RME device.
To switch from the dissolution phase 210 to the deposition phase 212, pulsed electrodeposition is used by applying pulsed voltage to the RME device. The applied pulsed voltage includes an “on” state, where voltage is applied, and an “off” state, where voltage is not applied. The frequency and duty cycle can be defined using the following equations:
where ton is the time the pulse is in the on state and toff is the time the pulse is in the off state.
Table 3 shows the haze from 400 nm to 750 nm of disclosed embodiments tinted to 10% transmission at various frequencies and duty cycles. Haze was calculated by dividing the diffuse by total transmission at each wavelength and taking the average over the wavelength at two locations.
Table 4 shows the color neutrality of disclosed embodiments tinted to 10% transmission at various duty cycles and frequencies. The color neutrality was determined by calculating chroma from values describing the brightness layer, the color on the red-green axis, and color on the blue-yellow axis. For a value of less than 10, the color of the material falls within the perception of grayscale for a human and is considered color neutral.
Table 5 shows the coloration efficiency of disclosed embodiments tinted at 10% transmission at different duty cycles and frequencies. Coloration efficiency is calculated using the transmission at the start and end of the deposition cycle and charge densities. The coloration efficiency is related to how much energy is required to tint the disclosed embodiments. The coloration efficiency is maximized for low duty cycles.
Table 6 shows the root mean squared (RMS) roughness measured in nanometers for disclosed embodiments tinted to 10% transmission at various duty cycles and frequencies. At a frequency of 0.1 Hz and a duty cycle of 10%, the RMS roughness is 13.70 nm while at a frequency of 10 Hz and a duty cycle of 10% the RMS roughness is 2.45 nm. As duty cycle increases, deposit diameters vary more than in lower duty cycles.
Table 7 shows calculated diffusion distance measured in millimeters for disclosed embodiments at various frequencies and duty cycles. The diffusion distance is proportional to the “on” state and inversely proportional to the square root of the frequency. Thinner layers at higher frequencies require less distance for the ions to travel from the bulk concentration which reduces effects of irregularities on the surface. Therefore, the metal cations are able to diffuse between the initial deposits and plate uniformly and smoothly on the surface.
Similar to
While pulsing ultimately results in faster tinting to a very low transmittance (e.g., 0.1%) privacy state, DC plating is faster in the initial stages of tinting, as shown in the Figures. As such, in an embodiment, to achieve the fastest tinting speed, the tinting protocol may include a DC plating step before pulsing. For example, in an embodiment, the DC plating time may be 5 seconds to 30 seconds, or about 10 seconds. Limiting the DC plating time ensures that the DC deposited film has not yet achieved a high surface roughness, and by switching to pulsing, the concentration profile can still adequately be restored. By way of example, such a combination tinting protocol (DC for about 10 seconds, followed by pulsing to the desired final transmittance) can reduces the total tinting time significantly (e.g., by 50-60% as compared to use of DC only, or by about 20-25% as compared to pulsing only, when tinting to a 0.1% privacy state transmittance. Such a reduction in tinting time makes such windows substantially more attractive to users. In addition, the reduction in how much metal is deposited and the avoidance of dendrites achieved with pulsing will greatly improve cycle life of such windows.
While certain embodiments of the present disclosure have been described in detail, with reference to specific configurations, parameters, components, elements, etcetera, the descriptions are illustrative and are not to be construed as limiting the scope of the claimed invention.
Furthermore, it should be understood that for any given element of component of a described embodiment, any of the possible alternatives listed for that element or component may generally be used individually or in combination with one another, unless implicitly or explicitly stated otherwise.
In addition, unless otherwise indicated, numbers expressing quantities, constituents, distances, or other measurements used in the specification and claims are to be understood as optionally being modified by the term “about” or its synonyms. When the terms “about,” “approximately,” “substantially,” or the like are used in conjunction with a stated amount, value, or condition, it may be taken to mean an amount, value or condition that deviates by less than 20%, less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount, value, or condition. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Ranges between any values disclosed herein are contemplated, and within the scope of the present disclosure.
Any headings and subheadings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims.
It will also be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” do not exclude plural referents unless the context clearly dictates otherwise. Thus, for example, an embodiment referencing a singular referent (e.g., “electrode”) may also include two or more such referents.
It will also be appreciated that embodiments described herein may also include properties and/or features (e.g., components, members, elements, parts, and/or portions) described in one or more separate embodiments and are not necessarily limited strictly to the features expressly described for that particular embodiment. Accordingly, the various features of a given embodiment can be combined with and/or incorporated into other embodiments of the present disclosure. Thus, disclosure of certain features relative to a specific embodiment of the present disclosure should not be construed as limiting application or inclusion of said features to the specific embodiment. Rather, it will be appreciated that other embodiments can also include such features.
This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 63/330,140 entitled PULSED ELECTRODEPOSITION FOR REVERSIBLE METAL ELECTRODEPOSITION TO CONTROL METAL FILM MORPHOLOGY AND OPTICAL PROPERTIES filed Apr. 12, 2022 and U.S. Provisional Patent Application Ser. No. 63/432,534 entitled PULSED ELECTRODEPOSITION FOR REVERSIBLE METAL ELECTRODEPOSITION TO CONTROL METAL FILM MORPHOLOGY AND OPTICAL PROPERTIES filed Dec. 14, 2022. Each of the foregoing applications is incorporated herein by reference in its entirety.
This invention was made with government support under grant no. 2127308 awarded by the National Science Foundation. The government has certain rights in the invention.
Number | Date | Country | |
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63330140 | Apr 2022 | US | |
63432534 | Dec 2022 | US |