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Vol. 17 (2025)

A Janus Smart Window for Temperature-Adaptive Radiative Cooling and Adjustable Solar Transmittance

https://doi.org/10.1007/s40820-025-01740-1
Zuowei Zhang
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Meina Yu
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Cong Ma
School of Materials Science and Engineering, Peking University, Beijing 100871, People’s Republic of China
Longxiang He
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Xian He
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Baohua Yuan
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Luoning Zhang
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Cheng Zou
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Yanzi Gao
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China
Huai Yang
Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, People’s Republic of China

Corresponding Author: Huai Yang

yanghuai@pku.edu.cn

Nano-Micro Letters, Vol. 17 (2025), Article Number: 233

Abstract

The advancement of sophisticated smart windows exhibiting superior thermoregulation capabilities in both solar spectrum and long-wave infrared range maintains a prominent objective for researchers in this field. In this study, a Janus window is proposed and prepared based on polymer-stabilized liquid–crystal films/thermochromic materials. It can achieve switchable front long-wave infrared emissivity (εFront) and solar modulation ability (ΔTsol) through dynamic flipping, making it suitable for different seasonal energy-saving requirements. Outdoor experiments show that under daytime illumination, the indoor temperature decreases by 8 °C, and the nighttime temperature drops by 5 °C. MATLAB simulation calculations indicate that the daytime cooling power is 93 W m−2, while the nighttime cooling power reaches 142 W m−2. Interestingly, by modifying the conductive layer, it can effectively shield electromagnetic radiation (within the X-band frequency range (8.2–12.4) GHz). Energy simulation reveals the substantial superiority of this device in energy savings compared with single-layer polymer-stabilized liquid crystal, poly(N-isopropyl acrylamide), and normal glass when applied in different climate zones. This research presents a compelling opportunity for the development of sophisticated smart windows characterized by exceptional thermoregulation capabilities.


Highlights:
1 Using polymer-stabilized liquid crystal as the active control layer and KCWO-PNIPAM (KPP) as the passive control layer, a KPP smart window was constructed, successfully achieving dual electro-thermal collaborative control.
2 The window can adjust incident light across three bands: visible light, near-infrared light, and mid-far infrared light (especially 8–13 µm).
3 Combination of active and passive control to meet the diverse weather conditions.

Keywords

Thermal insulation Solar modulation Photothermal conversion Radiative cooling Energy saving
Zhang, Zuowei, Meina Yu, Cong Ma, Longxiang He, Xian He, Baohua Yuan, Luoning Zhang, Cheng Zou, Yanzi Gao, and Huai Yang. 2025. “A Janus Smart Window for Temperature-Adaptive Radiative Cooling and Adjustable Solar Transmittance”. Nano-Micro Letters 17 (April):233. https://doi.org/10.1007/s40820-025-01740-1.
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