Visible‐to‐MIR broadband modulating electrochromic metal oxides‐based coating for thermal management

Abstract

The overheating/cooling of spacecraft solar cells under the contrastive temperature variation due to solar influence leads to severe consequences on both its performance and its long‐term stability. Radiative thermal management by broadband optical modulating coating provides a versatile and effective solution for spatial environments. Here we design a visible‐to‐mid‐infrared broadband modulating metal oxide‐based electrochromic coating for spacecraft solar cell thermal management. Upon impedance matching between multilayered architecture and control of crystallinity of WO3 with optimized morphology, the final coating successfully presents reversible transition from solar transmitter and thermal emitter to heat preserving coating with infrared (IR) stealth ability. The transmission spectrum of the coating in its bleached state fits the solar spectrum curve (0.3‐1.2 μm) for photocurrent harvesting and it transmits up to 88% at 450 nm, at the solar radiation peak. The average mid‐infrared (MIR) (2‐16 μm) emissivity of the coating is 80%, with a tunability of 20% in average. The demonstrated capabilities of broadband modulating electrochromic coating are highly promising for solar cell thermoregulation in space or terrestrial environments and also for IR‐stealth applications in the defense sector.

Wearable electrochromic materials and devices: from visible to infrared modulation

“…34,35 The widely used infrared-variable EC materials include tungsten oxides (WO 3 ) and conducting polymers, including polyaniline (PANI) and poly(3,4-ethylene dioxythiophene) (PEDOT). 36–38 In recent years, carbon nanomaterials such as multilayer graphene and carbon nanotubes (CNTs) were discovered for dynamic infrared modulation and showed high mechanical flexibility. 39 For instance, the EC devices with tunable infrared radiation based on flexible multilayer graphene thin films gated by a nonvolatile ionic liquid could achieve an 80% decrease of thermal emissivity from about 0.5 to a value below 0.1.…”

Multicolored Displays with Selective Visible‐Infrared Spectral Modulation for Optical Information Transmission

“…[ 3 ] It possesses the ability to change the apparent color in the visible region and modulate thermal emissivity in the infrared region. [ 4 ] The IR electrochromic material, including graphene, [ 5 ] MXene, [ 6 ] tungsten oxide (WO 3 ), [ 7 ] polyaniline (PANI), [ 8 ] and poly(3,4‐ethylene dioxythiophene) (PEDOT) [ 9 ] have been put forward. As a typical conducting polymer, PANI has attracted a great deal of attention due to its excellent emissivity modulation ability.…”

Infrared-Emissivity-Regulating Electrochromic Device with Low Visible Wavelength Absorption Based on Nanolayered Au/NiO/Ta2O5/WO3/Ge Photonic Structures

“…16 The heat absorbed by the ECD at the colored state is far greater than that dissipated by radiation, causing an adverse impact on the functions of the ECDs, even leading to the devices damage. 23 Therefore, how to obtain a high IR emissivity modulation of the ECDs, while maintaining high reflectivity in the entire solar spectrum range, remains a challenge. To this regard, construction of the microcavity in the ECDs could be a promising solution since it will not only block radiation from the sun but also offer better compatibility to the current ECDs, thus to achieve IR regulation ability that can reflect the entire solar spectrum.…”

“…It is noteworthy that for a spacecraft in the low earth orbit, environmental heating is largely caused by direct exposure to radiation from the sun, the sunlight reflected from the earth’s surface (earth’s albedo), and the IR radiation emitted from the earth (earthshine). − However, for ECDs, the device will being a high transmission (bleached) or high absorptivity (colored) state in the 250–2500 nm region under applied voltage . The heat absorbed by the ECD at the colored state is far greater than that dissipated by radiation, causing an adverse impact on the functions of the ECDs, even leading to the devices damage . Therefore, how to obtain a high IR emissivity modulation of the ECDs, while maintaining high reflectivity in the entire solar spectrum range, remains a challenge.…”