Ultrafast Switchable Passive Radiative Cooling Smart Windows with Synergistic Optical Modulation

Abstract

Switchable passive radiative cooling (PRC) smart windows can modulate sunlight transmission and spontaneously emit heat to outer space through atmospheric transparent window, presenting great potential in building energy conservation. However, realizing stable and on‐demand control of the cooling efficiency for PRC materials is still challenging. Herein, an electro‐controlled polymer‐dispersed liquid crystal (PDLC) smart window showing PRC property is designed and prepared by adding mid‐infrared emitting reactive monomers into the conventional PDLC matrix. It is found that not only the electro‐optical properties but also the PRC efficiency of PRC PDLC film are tunable by regulating the content of the mid‐infrared emitting components, film thickness, and micromorphology. This advanced PRC PDLC material achieves a near/sub‐ambient temperature when the solar irradiance is below 400 W m−2 and can dynamically manage daytime cooling efficiency. Importantly, its PRC efficiency is capable of being tuned in an on‐demand and ultrafast millisecond‐scale way, whose controllable transparency enables multistage heat regulation. This study is hoped to provide new inspiration in the preparation of advanced optical devices and energy‐efficient equipment.

Ultrafast Visible/Near‐Infrared Dual‐Band Selective Optical Switching via Polarization Control in Layered Low‐Symmetry TlSe

“…Various electrochromic devices commonly employed in smart windows utilize selective modulation in the visible‐NIR range. [ 10–13 ] However, they often rely on complex composite materials and require electrical control, leading to intricate structures and typically slow operation periods ranging from seconds to minutes. In contrast, TlSe, a single nanomaterial, is well‐suited for use in nanodevices and possesses inherent dual‐band selectivity without the need for an additional fabrication process.…”

“…Since smart windows typically require high transmission contrast, recently reported EC devices have demonstrated high modulation depths, approaching ≈99% at specific wavelengths. [ 86 ] However, their operation speeds typically fall in the range of seconds to tens of seconds, [ 10–13,85 ] making them less suitable for high‐speed processing of optical information signals. Furthermore, the fabrication of EC devices necessitates the integration of multiple components and most EC layers involve the integration of NIR‐active and visible‐active components to achieve dual‐band modulation, adding complexity to device structure and fabrication.…”

“…[ 3 ] Furthermore, it introduces novel functionalities in domains such as bio‐imaging, [ 7 ] food engineering, [ 8 ] and computer vision. [ 9 ] Thus, various dual‐band devices capable of selectively sensing [ 2,3,5 ] and modulating [ 10–13 ] visible‐infrared signals have been intensively developed. However, most existing visible‐infrared dual‐band modulators rely on electrochromic methods that typically operate on timescales of seconds to minutes, [ 10–13 ] which are unsuitable for processing ultrafast optical signals in the GHz‐THz frequency range.…”

“…[ 9 ] Thus, various dual‐band devices capable of selectively sensing [ 2,3,5 ] and modulating [ 10–13 ] visible‐infrared signals have been intensively developed. However, most existing visible‐infrared dual‐band modulators rely on electrochromic methods that typically operate on timescales of seconds to minutes, [ 10–13 ] which are unsuitable for processing ultrafast optical signals in the GHz‐THz frequency range. Furthermore, such devices often require a combination of multiple materials or structural elements for electrical control, leading to increased complexity in integrated systems.…”

Radiative cooling: structure design and application

“…Thermochromic smart windows can automatically control solar radiation according to the ambient temperature. 90–94 Smart windows with a radiative cooling effect have improved temperature regulation capabilities. Based on the phase transition properties of poly( N -isopropylacrylamide) (pNIPAm), Lin et al developed a solar and thermal regulatory thermochromic window, as shown in Fig.…”