A reversible metal electrodeposition-based radiative cooling-solar photothermal dynamic regulation device

Abstract

The application discloses a radiation refrigeration-solar photothermal dynamic regulation device based on reversible metal electrodeposition, wherein a super-transparent working electrode comprises an upper substrate, a semiconductor oxide conductive layer and a metal seed layer, and the reversible deposition and dissolution of an electrodepositable metal reflection layer can be realized by applying an external voltage; the gel electrolyte contains electrodepositable metal ions; and an absorber is provided with five layers of non-periodic multilayer films, which are stacked to form two groups of asymmetric Fabry-Pérot weak coupling resonant cavities. The application realizes cold and hot dual-mode regulation by switching the deposition / dissolution state of the metal reflection layer on the top super-transparent working electrode, and the regulation range of the solar absorption rate is not less than 0.8. The integrated and synergistic structure of the application can quickly complete the switching between cold and hot, and the temperature control performance is better than that of static refrigeration devices and commercial building materials. All the thin films are prepared by using a multi-target magnetron sputtering method without photolithography patterning, and are suitable for the passive thermal management of buildings and outdoor equipment throughout the year.

Description

Technical Field

[0001] This invention relates to the field of thermal radiation control technology, and more specifically to a dynamic control device for radiation cooling-solar photothermal energy based on reversible metal electrodeposition. Background Technology

[0002] The building sector accounts for over 30% of global energy consumption, with approximately 50% of that energy used for heating and cooling indoor spaces. These figures highlight the critical role of the building industry and the urgency of taking effective measures to reduce building energy consumption and carbon emissions. Therefore, reducing the energy consumption of building air conditioning systems for cooling and heating is a crucial step in reducing greenhouse gas emissions and achieving environmental protection goals. Against this backdrop, dynamic thermal management technology has attracted significant attention due to its ability to flexibly adjust system performance according to environmental changes, particularly radiative thermal management. This involves solar thermal collection in the solar radiation band and radiative cooling in the mid-infrared band, and these radiative mechanisms have significant application potential in building energy conservation. By dynamically adjusting the spectrum of materials, passive regulation of building energy consumption and thermal management can be achieved, lowering or raising the temperature of indoor spaces, thereby reducing the energy consumption of air conditioning systems.

[0003] Traditional solar heating devices, based on micro-nano structure designs, generate heat using solar radiation, while radiative cooling technology achieves cooling through radiative heat exchange between the Earth and outer space. However, most buildings operate in dynamically changing environments, including climate change, day-night cycles, and seasonal changes, leading to constant variations in outdoor temperatures and consequently, constantly evolving indoor environmental control requirements. Single-mode devices (solar heating only or daytime radiative cooling only) are limited in their effectiveness under such conditions. Therefore, designing dual-mode devices capable of switching between solar heating and radiative cooling would significantly improve energy efficiency in dynamic and complex environments. Combining solar heating with radiative cooling represents a competitive innovation direction.

[0004] In existing technologies, the dynamic switching between daytime radiative cooling (DRC) and solar heating (SH) is a key technology for achieving all-season thermal management of buildings and outdoor facilities. However, many existing SH / DRC switches can only switch between high transmittance and high reflectance of the solar spectrum, failing to efficiently collect solar energy or achieve in-situ, high-contrast state switching. Furthermore, existing devices often struggle to balance thermal management functionality with structural complexity, limiting their practical application in all-weather energy-saving scenarios.

[0005] To compensate for the shortcomings of single-mode devices and improve their energy utilization efficiency, scholars both domestically and internationally have conducted numerous studies on dual-mode devices combining solar heating and daytime radiative cooling. These studies on dynamic control of thermal radiation can be broadly categorized into four aspects: thermochromic control, mechanically driven thermochromic control, air humidity-driven thermochromic control, and electrochromic control. However, the first three control methods suffer from drawbacks such as slow control speed, poor spectral control effect, or inability to be specifically controlled according to human needs. In contrast, devices based on electrochromic control can reversibly change their transmittance or reflectance in the visible and infrared spectra under electrical stimulation, offering advantages such as faster switching speed, better switching effect, better robustness, and no moving parts.

[0006] Nevertheless, achieving synergistic multispectral modulation based on electrochromic properties remains challenging. On the one hand, it is difficult to obtain a wide spectral tuning range for overall performance; the solar absorptivity tuning range of existing mainstream devices is generally below 0.8, and the temperature control difference is small, failing to meet the requirements for all-weather, year-round use. On the other hand, when achieving color-changing switching through reversible electroplating, conductive electrodes are required to apply an external electric field, but it is difficult to achieve conductive electrodes that are transparent in the solar energy band. Although there are many methods for color-changing modulation to achieve solar heating and daytime radiative cooling, the effect on dual-mode devices that combine radiative cooling and solar thermal collection is still not good enough (most have a spectral tuning range of less than 80%), and there is a lack of complete device solutions that integrate broad-spectrum high absorption, reversible uniform electroplating, and low-cost mass production. Summary of the Invention

[0007] To address the problems of low solar modulation contrast and difficulty in efficiently collecting solar energy in existing SH / DRC switches, this invention aims to provide a dynamic control device for radiation cooling and solar thermal regulation based on reversible metal electrodeposition, offering a new solution for all-weather, adaptive thermal management technology.

[0008] The present invention discloses a reversible metal electrodeposition-based radiative cooling-solar thermal dynamic control device, comprising, from top to bottom, an ultra-transparent working electrode, a gel electrolyte layer, and a metamaterial absorber photonic electrode; the ultra-transparent working electrode comprises an upper substrate, a semiconductor oxide conductive layer, and a metal seed layer, capable of reversible electrodeposition and dissolution of an electrodeposable metal reflective layer by applying an external voltage; the gel electrolyte layer contains electrodeposable metal ions, filling the space between the ultra-transparent working electrode and the metamaterial absorber photonic electrode, providing a medium for reversible electrochemical reactions of the metal; the metamaterial absorber photonic electrode comprises a lower substrate and five non-periodic multilayer films, the five films being sequentially stacked as an ultrathin semiconductor oxide conductive layer, a top low-loss dielectric layer, a middle high-loss metal layer, a bottom low-loss dielectric layer, and a bottom high-loss metal layer, forming two sets of asymmetric Fabry-Pérot weakly coupled resonant cavities; the device switches between solar heating and daytime radiative cooling states by the deposition and dissolution of the metal reflective layer on the top ultra-transparent working electrode, with a solar absorptivity modulation range of not less than 0.8. In a preferred embodiment, the overall sheet resistance of the ultra-transparent working electrode is no higher than 1000 Ω / sq, enabling reversible electrodeposition and dissolution of the electrodeposable metal reflective layer through an applied voltage. This invention achieves reversible control of ultra-high solar energy absorption rates of 0.8 and above through a three-in-one integrated architecture comprising a low-resistivity transparent electrode with a metal seed layer, a gel electrolyte containing electrodeposable metal ions, and a five-layer asymmetric dual-weakly coupled FP resonant metamaterial absorber.

[0009] In a preferred embodiment, the semiconductor oxide conductive layer is selected from at least one of ITO and AZO, with a thickness ranging from 10 nm to 30 nm; the metal seed layer is selected from one or a combination of noble metals Pt, Au, and Pd, with a thickness ranging from 0.5 nm to 3 nm. In a preferred embodiment, MPTMS or APTMS organosilane modification molecules may be connected between the metal seed layer and the ITO layer to improve the adhesion between the metal seed layer and the substrate interface. By limiting the thickness range of the composite electrode of preferred semiconductor oxide and thin metal seed layer, this invention can simultaneously achieve both high light transmittance in the solar band and uniform electrodeposition of metal ions, avoiding the dual defects of thick metal blocking light and excessive sheet resistance of thin conductive layer, and achieving an unexpected effect of synergistic improvement in light transmittance, conductivity, and electroplating uniformity.

[0010] In a preferred embodiment, the top low-loss dielectric layer and the bottom low-loss dielectric layer are one or more of silicon dioxide, aluminum oxide, titanium dioxide, and silicon nitride; the top dielectric thickness is 20nm~100nm, and the bottom dielectric thickness is 80nm~135nm. This invention constructs an asymmetric dual-weakly coupled FP resonant cavity by using differential thicknesses of the upper and lower silicon dioxide dielectric layers. Combined with a high-loss platinum layer, this allows the two resonant cavities to capture short-wavelength and long-wavelength sunlight respectively, forming a continuous, flat, high-absorption platform, thus solving the inherent defects of narrow absorption bandwidth and low absorption peak value in a single FP cavity.

[0011] In a preferred embodiment, the thickness of each film layer in the photonic electrode of the metamaterial absorber is determined according to the phase-matching formula Δφ. tot =2Δφ prop +Δφ refl The resonant frequency is calculated using 2Nπ (where N is an integer) and then optimized. The two resonant cavities independently generate absorption peaks, which then merge to form a flat, broad absorption plateau. This invention constructs an asymmetric, weakly coupled cavity by specifically optimizing the thickness of the upper and lower dielectric layers based on a phase-matching formula. This allows for precise control of the resonant positions of the two resonant cavities, achieving multi-band solar energy absorption and ensuring stable, batch-reproducible, broad-spectrum high absorption performance.

[0012] In a preferred embodiment, the electrodepositable metal ion is silver ion; the average absorptivity in the solar heating state is not less than 0.9, the average absorptivity in the daytime radiation cooling state is not more than 0.1, and the average solar reflectivity in the cooling state is not less than 0.9. Besides silver ions, copper ions can also be used as electrodepositable metal ions to achieve the dual-mode modulation effect of this invention, with only a slight difference in the spectral reflectance threshold. This invention, through an asymmetric dual FP absorption cavity and a reversible silver mirror electrode synergistic spectral modulation system, can stably achieve reversible switching between the two extreme limits of high absorption and high reflectivity in the solar band, achieving an ultra-large spectral modulation amplitude of over 0.8, overcoming the industry pain point of insufficient contrast control in thermochromic and conventional electrochromic devices.

[0013] In a preferred embodiment, the time for the device to switch from solar heating to daytime radiative cooling does not exceed 20 minutes, and the steady-state temperature of the device after the switch is lower than the ambient air temperature. This invention enhances the deposition and dissolution reaction kinetics of electrodeposable metals through a thin seed layer, combined with a low-impedance transparent conductive system, enabling rapid switching between hot and cold states. Existing static DRCs lack this switching capability, while this invention can dynamically adjust its thermal management strategy in real time according to day / night cycles and seasonal light conditions.

[0014] In a preferred embodiment, the steady-state temperature under solar heating is 14°C to 19°C higher than the ambient temperature; the steady-state temperature under daytime radiative cooling is 2°C to 8°C lower than the ambient temperature. This invention, through ultra-large spectral modulation amplitude combined with continuous mid-infrared radiation, can simultaneously achieve wide-range in-situ passive heat collection and heating, and passive sub-environmental cooling. Traditional single-function heat absorption and cooling building materials can only provide unidirectional temperature control; this invention's single device meets the year-round heating and cooling control needs.

[0015] In a preferred embodiment, the two sets of asymmetric Fabry-Pérot weakly coupled resonant cavities formed by the five-layer aperiodic multilayer film achieve high absorption across the entire 0.3~2.5μm wavelength range, while the ultra-transparent working electrode substrate exhibits high emission characteristics in the 4~16μm mid-infrared band. Under the same illumination conditions, the steady-state temperature of the device in its cooled state is lower than that of a static radiation-cooled sample with only a single cooling function. The temperature rise in its solar-heated state is higher than that of commercial black bricks, and the temperature drop in its daytime radiation-cooled state is better than that of commercial white bricks. This invention achieves full-band solar energy capture and high infrared emission from the top substrate through asymmetric dual weakly coupled resonant cavities, simultaneously maximizing solar heat collection and all-weather infrared radiation heat dissipation, thereby generating a temperature control gain superior to static DRC and commercial black and white bricks.

[0016] In a preferred embodiment, regardless of whether it is in solar heating mode or daytime radiative cooling mode, the device can continuously radiate heat to outer space through an 8μm~13μm atmospheric window, maintaining its radiative heat dissipation capability around the clock.

[0017] In a preferred embodiment, the gel electrolyte is composed of a metal salt, a bromine-based complexing agent, an organic matrix, and a polar organic solvent; the metal salt is a silver salt, the bromine-based complexing agent is tetrabutylammonium bromide, the organic matrix is ​​polyvinyl butyral, and the polar organic solvent is dimethyl sulfoxide. This invention uses polyvinyl butyral as the gel matrix to solidify the electrolyte, and combines it with tetrabutylammonium bromide as a silver ion complexing agent to form a stable gel electrolyte in a wide-window dimethyl sulfoxide solvent system. This solves the defects of existing liquid electrolytes, such as easy leakage, uneven silver film deposition thickness, and poor cycle performance, and provides better device packaging stability and electrodeposition uniformity.

[0018] This invention employs a low-resistivity ultra-transparent electrode comprising a semiconductor oxide conductive layer and a metal seed layer, paired with a gel electrolyte containing electrodeposable metal ions. It combines a five-layer aperiodic, double-asymmetric Fabry-Pérot weakly coupled resonant absorption integrated synergistic architecture formed by alternating stacks of semiconductor oxide conductive layers, high- and low-loss dielectrics, and high-loss metals. By relying on an external voltage to control the reversible deposition and dissolution of the electrodeposable metal reflective layer on the top working electrode, it effectively solves the technical shortcomings of existing dynamic photothermal control devices, such as difficulty in simultaneously achieving ultra-high solar spectral modulation amplitude and all-weather synchronous infrared radiation heat dissipation, slow mode switching response speed, unidirectional temperature control only, and complex large-scale fabrication processes. This is achieved through two sets of thickness-differential resonant... The cavity captures sunlight in different wavelengths, achieving reversible switching of solar absorptivity of 0.8 or higher. It maintains high emission performance in the mid-infrared band in both heating and cooling modes, and can dynamically switch between hot and cold states in a short time. Under the same outdoor illumination conditions, its heat collection and heating effect is superior to traditional commercial heat-absorbing building materials, and its passive cooling performance exceeds that of static radiation cooling devices. The entire set of functional thin films can be formed using only conventional multi-target magnetron sputtering, without the need for photolithography and patterned micro-processing. It has achieved unexpected comprehensive technical effects in broadening the spectral control range, improving adaptability to all-season environments, simplifying the production process, and reducing manufacturing costs. It can be widely adapted to building envelopes and year-round intelligent passive thermal management scenarios for outdoor equipment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a radiation-cooling-solar-thermal dynamic control device based on reversible metal electrodeposition according to a preferred embodiment of the present invention.

[0020] Figure 2 yes Figure 1 A schematic diagram of the assembly of a radiation cooling-solar photothermal dynamic control device.

[0021] Figure 3 yes Figure 1 The structural design process and measured spectral characteristics of the photonic electrode of the metamaterial absorber in the radiative cooling-solar photothermal dynamic control device.

[0022] Figure 4 yes Figure 1 Measured optical reflection spectral characteristics of the top ultra-transparent working electrode of the radiation-cooling-solar-thermal dynamic control device under native silver-free deposition state.

[0023] Figure 5 A comparison of the absorption rates of dual-mode spectra to fully cover the solar energy band and the mid-infrared thermal radiation band.

[0024] Figure 6 Record the complete set of outdoor test results of the device of this invention, which was continuously measured for 6 hours on an outdoor test bench in Shanghai during the winter and spring seasons. Detailed Implementation

[0025] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0026] like Figure 1 As shown, a preferred embodiment of the radiative cooling-solar thermal dynamic control device based on reversible metal electrodeposition according to the present invention includes an upper ultra-transparent working electrode, a middle gel electrolyte, and a lower metamaterial absorber photonic electrode arranged sequentially from top to bottom.

[0027] The working electrode is located at the top and includes a semiconductor oxide conductive layer and an ultrathin metal layer processed on the upper substrate. This layer simultaneously maintains high transparency and conductivity in the solar energy band. By controlling the external voltage applied to the working electrode, reversible deposition (i.e., electroplating) and dissolution of the metal can be achieved on the electrode. Reversible metal electrodeposition controls the reflection and absorption of energy in the solar energy band, thereby achieving broadband dynamic switching / modulation. This overcomes the shortcomings of traditional electrochromic technology, which suffers from high absorption in the solar energy band and imperfect spectral modulation. In a preferred embodiment, the upper substrate is one or more of quartz, glass, and PET film. In a preferred embodiment, the semiconductor oxide conductive layer is one or more of ITO and AZO, with a thickness between 10 nm and 30 nm. In a preferred embodiment, the metal layer is a noble metal element such as Pt, Au, or Ti, with a thickness between 0.5 nm and 2 nm. This layer serves as a seed layer for metal deposition, improving the growth quality and uniformity of the reversibly electrodeposited metal reflective layer. It can be connected to MPTMS and APTMS molecular layers that do not participate in spectral modulation but only modify the substrate. In this embodiment, the upper substrate is quartz glass, the semiconductor oxide conductive layer is ITO, and the metal layer is Pt. Both ITO and Pt are processed using multi-target magnetron sputtering technology. It should be understood that nanoscale ultrathin ITO is itself a highly transparent conductive material in the solar light band, and the 0.5~3nm ultrathin Pt seed layer also has high transmittance to sunlight, thus forming an ultra-transparent working electrode.

[0028] The electrolyte is sandwiched between the working electrode and the absorber, and is used to achieve reversible electrodeposition of the metal reflective layer based on an electrochemical reaction. In a preferred embodiment, the electrolyte includes a gel electrolyte and an encapsulation material. In a preferred embodiment, the gel electrolyte is composed of ionic reactants, an organic matrix, and a solvent. In a preferred embodiment, the ionic reactants are silver ions (Ag). + ), divalent copper ions (Cu) 2+ ), bromide ions (Br) -One or more of the following: In a preferred embodiment, the organic matrix is ​​one or more of polyvinyl alcohol, polyvinyl butyral, and polyethylene oxide. In a preferred embodiment, the solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, and water. In a preferred embodiment, the encapsulating material is one or more of silicone, rubber, and acrylic hollow gasket.

[0029] The absorber photoelectric electrode is a bottom-mounted photoelectrode employing a subwavelength multilayer metamaterial structure. This structure comprises a non-periodic multilayer film system fabricated on a lower substrate. This multilayer film system consists of five layers, from top to bottom: a semiconductor oxide conductive layer, a top low-loss dielectric layer, a middle high-loss metal layer, a bottom low-loss dielectric layer, and a bottom high-loss metal layer. The metamaterial absorber achieves ultra-wideband (0.3~2.5μm) solar high-absorption optical characteristics based on the weak coupling effect of dual Fabry-Pérot resonances. In a preferred embodiment, the lower substrate is one or more of quartz, glass, and PET film. In a preferred embodiment, the semiconductor oxide conductive layer is one or more of ITO and AZO, with a thickness between 10nm and 30nm. In a preferred embodiment, the top and bottom dielectric layers are made of one or more of SiO2, TiO2, HfO2, and Al2O3. In a preferred embodiment, the thickness of the top dielectric layer is between 20 and 100 nm, and the thickness of the bottom dielectric layer is between 80 and 135 nm. The two sets of resonant cavities each generate independent absorption peaks, which are then superimposed and merged, significantly broadening the solar absorption bandwidth by 0.3–2.5 μm, unlike the narrow-band absorption of a single FP cavity. In this embodiment, SiO2, which has high optical transparency in the solar band, is selected as the material for both the top and bottom dielectric layers. In a preferred embodiment, the materials for the intermediate high-loss metal layer and the bottom high-loss metal layer are one or more of Pt, W, Ti, and Cr, with a thickness of 2–15 nm. In this embodiment, Pt, which has high electromagnetic loss characteristics in the solar band, is selected as the material for both the intermediate and bottom metal reflective layers. In this embodiment, the lower substrate is quartz glass, and the dual-resonance five-layer aperiodic film system includes, from top to bottom, an ITO conductive layer, a top SiO2 dielectric layer, a Pt intermediate metal layer, a bottom SiO2 dielectric layer, and a bottom Pt metal layer. Broadband light absorption is achieved by weak coupling of dual Fabry-Pérot resonances. ITO, Pt, and SiO2 are all processed by multi-target magnetron sputtering technology.

[0030] The working principle of the radiative cooling-solar thermal dynamic control device in this embodiment is based on a reversible metal electroplating system. When a negative voltage is applied to the working electrode, the metal in the electrolyte, such as silver ions (Ag), reacts. +Electrons are gained on the surface of the metal layer of the working electrode, forming a uniform and dense Ag film, thereby switching the device to radiative cooling mode. In this mode, the Ag film has a relatively high reflectivity, which can reflect the energy of the solar spectrum; at the same time, the substrate, such as quartz glass, has a high emissivity in the 4μm~16μm infrared region, which can emit heat as thermal radiation through the 8μm~13μm atmospheric window. The cooling mode can reduce the temperature by 2~8℃ compared to the ambient temperature, which is more than 3℃ higher than commercial white cooling bricks. When a positive voltage is applied, the deposited Ag film undergoes an oxidation reaction on the metal layer of the working electrode and is oxidized into Ag. + It dissolves in the electrolyte, thus switching the device to solar heating mode. In this mode, in the 0.3-2.5μm band, both the working electrode and the electrolyte have low reflectivity and high transmittance, allowing most of the energy in the solar spectrum to enter the absorber and be utilized. This can raise the temperature by 14-19°C compared to the environment, which is 7-10°C higher than that of commercial black heat-absorbing bricks.

[0031] Thus, this invention combines reversible metal electrodeposition with the design of a dual Fabry-Pérot resonant five-layer film metamaterial micro / nano structure, enabling dynamic switching of thermal radiation between high reflectivity and high absorptivity. The solar absorptivity modulation range ΔAsol≈0.82 achieves broadband dynamic modulation of the solar spectrum, resulting in electrochromic thin film devices with superior solar heat collection and radiative cooling effects.

[0032] Figure 2 Show Figure 1 The fabrication method of a radiation-cooling-solar-thermal dynamic control device is presented. The left side is an exploded view of the device, showing three independent components in sequence: an ultra-transparent top working electrode, a hollow sealing gasket (i.e., a washer), and a metamaterial absorber photonic electrode. The middle view shows the process of injecting gel electrolyte into the sandwich layer after the upper and lower electrodes are aligned and assembled with the gasket, using a syringe. The right side view shows the complete finished device after gel injection and sealing. Specifically, clean upper and lower substrates are coated using micro-nano processing methods such as multi-target magnetron sputtering, then assembled using an insulating gasket in the middle. Finally, a gel electrolyte is injected through the side gaps into the working electrode and absorber using a syringe to complete the encapsulation. The device has a three-layer sandwich stacked structure, consisting of a top ultra-transparent working electrode, a middle layer of gel electrolyte, and a bottom layer of metamaterial absorber photonic electrode, all assembled and sealed with a gasket. All thin films are fabricated using only multi-target magnetron sputtering, eliminating the need for photolithography and patterned micro-processing steps, simplifying the micro-nano fabrication process and saving the high-cost photolithography step.

[0033] Specifically, the preparation method includes: S1, selecting a substrate and preparing a metamaterial absorber photonic electrode based on multi-target magnetron sputtering; S2, selecting a substrate and sequentially depositing a transparent oxide electrode and an ultrathin seed layer on one side of the substrate based on multi-target magnetron sputtering to obtain an ultra-transparent working electrode; S3, preparing a gel electrolyte for realizing the electrodeposition of a reversible metal reflective layer; S4, connecting the metamaterial absorber photonic electrode obtained in S1 and the ultra-transparent working electrode obtained in S2 through an encapsulation material, injecting the gel electrolyte prepared in S3 into the space between the two electrodes, and sealing it to obtain a radiative cooling-solar photothermal dynamic control device based on reversible metal electrodeposition.

[0034] In a preferred embodiment, quartz glass with a thickness of 1 mm and dimensions of 5 cm × 5 cm is selected as the top and bottom substrates, and is sequentially cleaned with acetone, isopropanol, and deionized water, and then dried under a nitrogen flow. The bottom conductive oxide layer is made of ITO, and the resonant absorber is a multilayer film structure composed of alternating Pt / SiO2 layers, fabricated using multi-target magnetron sputtering / plasma-enhanced chemical vapor deposition. The top conductive layer is an ITO / Pt bilayer structure, fabricated using multi-target magnetron sputtering. The electrolyte composition includes silver nitrate (AgNO3), tetrabutylammonium bromide (TBABr), dimethyl sulfoxide (DMSO), and polyvinyl butyral (PVB), sandwiched between the working electrode and the bottom transparent electrode.

[0035] Figure 3 yes Figure 1 The structural design process and measured spectral characteristics of the photonic electrode of the metamaterial absorber in a radiation-cooled-solar-thermal dynamic control device are shown in the left sub-figure. The horizontal axis represents wavelength (nm), and the vertical axis represents optical absorptivity A and total phase φ of the dielectric layer. tot The orange curve in the figure represents the total phase φ inside the top SiO2 dielectric layer in the four-layer aperiodic SiO2 / Pt / SiO2 / Pt film system. tot The blue curve represents the total phase φ inside the bottom SiO2 dielectric layer. totA significant difference in phase change exists between the upper and lower dielectrics, visually demonstrating the weak coupling characteristics of the two Fabry-Pérot resonant cavity structures, exhibiting asymmetry and phase mismatch. The solid black line represents the optical absorptivity curve of the stacked four-layer aperiodic film system, maintaining a high absorption plateau in the visible and near-infrared range of 500nm to 1500nm, corresponding to the broadband absorption effect of the dual resonant cavity capturing photons in different wavelength bands. The two arrows point to the cross-sectional electric field distribution cloud maps corresponding to the characteristic wavelengths of 500nm and 1000nm, respectively. The color from red to blue represents the electric field intensity from high to low. The short-wavelength electromagnetic field at 500nm is mainly localized in the top SiO2 dielectric cavity, while the long-wavelength electromagnetic field at 1000nm is mainly localized in the bottom SiO2 dielectric cavity, confirming the design concept of confining the electromagnetic field within the top and bottom dielectric materials of the two independent FP cavities, respectively. All thickness parameters of this film system are obtained through the phase matching formula: Δφ tot =2Δφ prop +Δφ refl The resonant frequency was calculated using the formula 2Nπ (N=0,1,2,…) and then optimized to determine the thickness of the Pt and SiO2 layers. The right sub-figure shows the horizontal axis covering the entire solar energy band from 0 to 2500 nm, and the vertical axis representing optical absorptivity. The solid red line represents the measured absorption spectrum of the actual fabricated metamaterial absorber photonic electrode sample, while the dashed red line represents the theoretically calculated spectrum obtained through simulation using the transfer matrix method and phase-matching formula. The overall trends, absorption peak positions, and absorption bandwidths of the two curves highly overlap, with only minor variations in the measured process at longer wavelengths, demonstrating that the film thickness design scheme can be replicated. Weighted integration calculations in the 0.3–2.5 μm solar energy band show that the average solar absorptivity of the actually fabricated metamaterial absorber photonic electrode reaches 0.87, fully validating the technical advantages of the four-layer aperiodic dual-FP cavity film system for broadband and efficient light collection.

[0036] Figure 4 yes Figure 1 The optical reflectance spectra of the top ultra-transparent working electrode of the radiative cooling-solar thermal dynamic control device under native silver-free deposition conditions were measured. In the spectral reflectance curve, the horizontal axis represents the wavelength of sunlight, and the vertical axis represents the spectral reflectance. The solid blue line represents the measured reflectance spectrum of the actual sample of the ultrathin ITO / Pt seed layer composite electrode; the dashed blue line represents the theoretical simulation spectrum obtained based on the thin-film optical transfer matrix method. The overall trend of the measured solid line and the theoretical calculation dashed line highly coincides, proving that the optical design model of the ultrathin ITO and ultrathin Pt seed layer micro-nano film is accurate, and the actual prepared sample can stably achieve low reflectance and high transmittance. The measured sheet resistance of the ultrathin ITO and Pt seed layer is ~668Ω / sq, which meets the electrode conductivity requirements of reversible metal electrodeposition (≤1000Ω / sq), and can uniformly conduct the applied voltage, ensuring uniform and reversible deposition and dissolution of the silver film.

[0037] Figure 5A dual-mode spectral absorbance comparison chart, fully covering the solar and mid-infrared thermal radiation bands, is used to demonstrate the spectral modulation performance of the device in two operating modes: solar heating (SH) and daytime radiative cooling (DRC). The average solar absorbance A is shown below. sol It was calculated by weighted integration of the spectrum in the wavelength range of 0.3-2.5 μm at AM1.5:

[0038]

[0039] Among them, A sol α(λ) is the average absorptivity of solar energy, representing the percentage of solar energy absorbed. α(λ) is the spectral absorptivity, calculated using the TMM (Transient Metal Mechanism) method, where A = 1 - TR. IDirect(λ) is the energy of solar energy that passes through the atmosphere and reaches the Earth's surface.

[0040] In the 0.3–2.5 μm solar wavelength range, the entire curve of the SH heated state (red line) maintains a high absorptivity of over 0.75 for an extended period. The weighted average solar absorptivity A is indicated by this curve. sol =0.91, meaning that most of the sunlight is captured and converted into heat energy by the underlying metamaterial absorber, meeting the heat collection and heating needs under cold conditions such as winter. The DRC cooling state (blue line) maintains an extremely low absorptivity across the entire wavelength range, with the weighted average solar absorptivity A marked. sol =0.09, the top silver film reflects and blocks the vast majority of sunlight, significantly reducing heat absorption by the device and achieving passive cooling during the day. The difference in average solar absorptivity between the two states is ΔA. sol With a value of approximately 0.82, it is far superior to existing in-situ switching technologies for thermal radiation characteristics such as electrochromic and thermochromic, and can quickly and in-situ switch between SH and DRC states.

[0041] In the 4~16μm mid-infrared radiation cooling band, the overall absorption rate remains high, and the two curves are highly overlapping with each other, with no obvious difference. This indicates that regardless of whether the device is in heat collection mode or reflective cooling mode, the top quartz substrate can efficiently radiate infrared heat to outer space. The cooling and heat dissipation capabilities are not affected by the silver reflective film, and the device has basic radiation heat dissipation performance in all weather conditions.

[0042] Thus, the device of this invention can achieve reversible switching of an ultra-wide absorptivity range of 0.09~0.91 in the solar energy band: the SH state relies on high absorption (A... sol =0.91) to complete photothermal heat collection, the DRC state relies on high solar reflectance (R sol ≈0.91) Suppress solar heat absorption and switch between heat collection and cooling as needed throughout the season; both working states maintain high infrared emission capability in the mid-infrared atmospheric window, and the cooling function is not limited by mode switching.

[0043] Figure 6This document records the complete set of outdoor experimental results of the device of this invention, which was continuously tested for 6 hours on an outdoor test bench in Shanghai during winter and spring. It includes four independent sub-figures, which cover four major test dimensions: all-weather long-term temperature control, multiple rounds of cold and hot state cycle comparison, spectral characteristic benchmarking, and horizontal comparison with commercial bricks and tiles.

[0044] The top left subplot shows the continuous outdoor temperature test curve for 6 hours from 12:00 to 18:00. The horizontal axis represents the test time (hour:minute, HH:MM), the left vertical axis represents the temperature T (°C), and the right vertical axis represents the solar irradiance. The yellow filled area represents the period with solar irradiance. The blue solid line represents the sample temperature of the device of this invention, and the orange solid line represents the ambient air temperature. The attached figure includes photographs of the device in both solar heating (SH) and daytime radiative cooling (DRC) states. During midday in Shanghai during winter and spring, the instantaneous total solar irradiance is approximately 500 W / m². 2 With an ambient relative humidity of 26.1%, the device was in SH solar heating mode, with a peak temperature increase of 18.6°C compared to the ambient temperature. Applying a reverse voltage to switch to DRC radiative cooling mode, the device could return from the high-temperature SH state to a sub-ambient cooling state below the ambient temperature in just 20 minutes. Under daytime solar irradiation, the DRC mode could achieve a maximum temperature drop of 6.4°C below the ambient temperature; in the evening, when there was no strong solar irradiation, the device in cooling mode could achieve an ambient temperature drop of 8.2°C, proving that the device can stably complete passive radiative cooling both day and night.

[0045] The upper right subfigure shows a daytime cycle comparison test between the dynamically switching device of this invention and the static DRC sample. The horizontal axis represents the time interval from 10:00 to 13:00, the left vertical axis represents temperature, and the right vertical axis represents solar irradiance. The blue curve represents the device of this invention that can switch between SH and DRC, the gray curve represents the static DRC control sample with only a single cooling function, and the orange curve represents the ambient temperature. The experiment completed two full SH heating → DRC cooling cycles: under the two SH solar heating conditions, the device temperature rose by 13.5℃ and 15.9℃ compared to the ambient temperature, respectively; after switching to DRC cooling mode, the dynamic device of this invention achieved an additional sub-ambient temperature drop of 1.1℃ to 1.9℃ compared to the static DRC sample, demonstrating the performance advantage of the reversible dual-mode structure of this invention compared to traditional static cooling devices.

[0046] The lower left subfigure shows a comparison of the solar spectrum of the device with commercial black and white bricks. The horizontal axis represents the wavelength of the entire solar spectrum from 0.3 to 2.5 μm. The image is divided into two sets of curves: the upper part is the spectral absorbance curve, with the solid black line representing the device in the SH heating state and the dashed black line representing the commercial heat-absorbing black brick; the lower part is the spectral reflectance curve, with the solid light gray line representing the device in the DRC cooling state and the dashed light gray line representing the commercial cooling white brick. The inset shows physical samples of the device, black brick, and white brick, with a scale bar of 1 cm. The spectral curves clearly demonstrate that the solar absorption capacity of the present invention in the heating mode is superior to that of the commercial black brick, and the solar reflectance capacity in the cooling mode is superior to that of the commercial white brick.

[0047] The lower right subplot shows a comparison test of the device with commercial black and white bricks for synchronous outdoor temperature control. The horizontal axis represents time (11:00-13:00), the left vertical axis represents temperature, and the right vertical axis represents solar irradiance. Blue represents the dynamically controlled device of this invention, black represents commercial black bricks, gray represents commercial white bricks, and orange represents ambient temperature. The solar irradiance under the test conditions was approximately 800 W / m². 2 In SH solar heating mode, the device heats up 25.2°C compared to the environment, and 10.1°C more than commercial black bricks. After switching to DRC radiative cooling mode, the device achieves an additional 3.2°C temperature drop compared to commercial white bricks. A horizontal quantitative comparison with traditional building bricks and tiles fully demonstrates that the device of this invention has a comprehensive leading performance in both heat collection and cooling.

[0048] This invention precisely integrates reversible metal electrodeposition technology with optical metamaterial absorbers, and relies on optical control mechanisms such as the reversible deposition and dissolution of silver mirrors to achieve control over the solar energy absorption rate by the amplitude ΔA. sol ~0.82, this ultra-large spectral modulation amplitude is difficult to achieve with existing electrochromic, thermochromic and other traditional dynamic thermal control technologies, which significantly improves the thermal control capability and all-season environmental adaptability of the device.

[0049] Compared to traditional solar absorbers or static radiative coolers with only a single function, this invention relies on an electrochemical reversible silver deposition / dissolution mechanism to possess in-situ, active, and reversible dual-mode dynamic switching function. It can optimize thermal management strategies in real time according to environmental conditions such as seasonal changes, day-night cycles, and sunlight intensity. In solar heating mode, the device can efficiently capture solar energy, achieving a significant temperature rise of 14-19°C compared to the ambient temperature, fully utilizing solar energy for passive heat collection and heating. In daytime radiative cooling mode, it can significantly suppress solar heat absorption, achieving passive cooling without energy consumption through an infrared atmospheric window, reaching a sub-ambient temperature drop of 2-8°C. This dual reversible control function completely overcomes the limitations of traditional passive thermal management devices, which are limited by their single function and inability to adapt to all seasonal conditions, providing a new technological paradigm for building energy conservation and intelligent thermal regulation of outdoor facilities.

[0050] The invention features a simple overall structure and does not require complex photolithography, micro-nano patterning, or other high-precision and high-cost microfabrication processes. It can accurately prepare various functional thin films using only conventional multi-target magnetron sputtering vacuum deposition technology, which greatly reduces the difficulty of device fabrication and production costs. At the same time, it has good process compatibility, strong reproducibility, and excellent potential for large-scale expansion, and can be widely adapted to large-scale energy-saving applications in various scenarios such as building envelopes and outdoor electrical equipment.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A dynamic control device for radiation-cooled solar thermal energy based on reversible metal electrodeposition, characterized in that, The ultra-transparent working electrode, the gel electrolyte layer, and the metamaterial absorber photonic electrode are stacked from top to bottom; The ultra-transparent working electrode comprises an upper substrate, a semiconductor oxide conductive layer, and a metal seed layer, and can achieve reversible electrodeposition and dissolution of an electrodeposable metal reflective layer by applying an external voltage. The gel electrolyte layer contains electrodeposable metal ions, which fill the space between the ultra-transparent working electrode and the metamaterial absorber photonic electrode, providing a reversible metal electrochemical reaction medium. The metamaterial absorber photonic electrode comprises a lower substrate and five non-periodic multilayer films. The five films are stacked sequentially by an ultrathin semiconductor oxide conductive layer, a top low-loss dielectric layer, a middle high-loss metal layer, a bottom low-loss dielectric layer, and a bottom high-loss metal layer to form two sets of asymmetric Fabry-Pérot weakly coupled resonant cavities. The device switches between solar heating and daytime radiation cooling states by depositing and dissolving a metal reflective layer on the top ultra-transparent working electrode, with the solar absorption rate adjustable by no less than 0.

8.

2. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The semiconductor oxide conductive layer is selected from at least one of ITO and AZO, with a thickness ranging from 10nm to 30nm; the metal seed layer is selected from one or a combination of noble metals such as Pt, Au, and Pd, with a thickness ranging from 0.5nm to 3nm.

3. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The top low-loss dielectric layer and the bottom low-loss dielectric layer are one or more of silicon dioxide, aluminum oxide, titanium dioxide, and silicon nitride; the top dielectric thickness is 20nm~100nm, and the bottom dielectric thickness is 80nm~135nm.

4. The radiative cooling-solar thermal dynamic control device according to claim 3, characterized in that, The thickness of each film layer in the photonic electrode of the metamaterial absorber is based on the phase matching formula Δφ tot =2Δφ prop +Δφ refl =2Nπ (N is an integer) is used to calculate the resonant frequency and then optimize it. The two sets of resonant cavities independently generate absorption peaks and merge to form a flat and wide absorption plateau.

5. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The electrodeposable metal ion is silver ion; the average absorptivity in the solar heating state is not less than 0.9, the average absorptivity in the daytime radiation cooling state is not more than 0.1, and the average solar reflectivity in the cooling state is not less than 0.

9.

6. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The time required for the device to switch from solar heating to daytime radiative cooling is no more than 20 minutes, and the steady-state temperature of the device after the switch is lower than the ambient air temperature.

7. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The steady-state temperature under solar heating is 14℃~19℃ higher than the ambient temperature; the steady-state temperature under daytime radiative cooling is 2℃~8℃ lower than the ambient temperature.

8. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The two sets of asymmetric Fabry-Pérot weakly coupled resonant cavities formed by the five non-periodic multilayer films can achieve high absorption across the entire wavelength range of 0.3~2.5μm, and the ultra-transparent working electrode substrate exhibits high emission characteristics in the mid-infrared band of 4~16μm. Under the same illumination conditions, the steady-state temperature of the device in the cooling state is lower than that of the static radiation cooling sample with only a single cooling function. The temperature rise in the solar heating state is higher than that of commercial black bricks, and the temperature drop in the daytime radiation cooling state is better than that of commercial white bricks.

9. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, Whether in solar heating mode or daytime radiative cooling mode, the device can continuously radiate heat into outer space through an 8μm~13μm atmospheric window, maintaining its radiative heat dissipation capability around the clock.

10. The radiative cooling-solar thermal dynamic control device according to claim 1, characterized in that, The gel electrolyte is composed of a metal salt, a bromine complexing agent, an organic matrix, and a polar organic solvent; the metal salt is a silver salt, the bromine complexing agent is tetrabutylammonium bromide, the organic matrix is ​​polyvinyl butyral, and the polar organic solvent is dimethyl sulfoxide.

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