Transparent Radiative Cooling Films Based on Dendritic Silica for Room Thermal Management

Abstract

Building energy consumption accounts for 40% of global energy use, with a large part attributed to windows. Transparent radiative cooling (TRC) coatings integrate transparency and radiative cooling, offering a promising solution. In this study, the transparency constraint and selective transmittance spectra of TRC films were proposed according to the heat transfer equation. On the basis of these rules, we designed a flexible TRC film composed of an emission layer, an ITO coating, a flexible substrate, and an adhesive layer from top to bottom. An ultrathin emission layer (~10 μm) with dendritic mesoporous silica nanoparticles embedded in polydimethylsiloxane was fabricated via a low-cost blade coating process suitable for manufacturing production. The film exhibited high visible light transmittance, ultraviolet blocking ability, and ultrahigh infrared emissivity. In addition, it provides benefits such as hydrophobicity and electromagnetic interference shielding. The results of outdoor tests revealed that a maximum cooling temperature of 12.6°C can be reached during sunny days. The theoretical cooling power reaches 99.25 W/m² at 27°C ambient temperature, making this TRC film a potential sustainable solution for room thermal management and energy efficiency.

Keywords

Dendritic silica / energy efficiency / thermal management / transparent radiative cooling

References

[1] J. Liang, J. Wu, J. Guo, et al., “Radiative Cooling for Passive Thermal Management Towards Sustainable Carbon Neutrality,” National Science Review 10 (2023): nwac208.

[2] S. Shi, P. Lv, C. Valenzuela, et al., “Scalable Bacterial Cellulose-Based Radiative Cooling Materials With Switchable Transparency for Thermal Management and Enhanced Solar Energy Harvesting,” Small 19 (2023): 2301957.

[3] Z. Yang, Y. Lu, Z. Wang, et al., “Recent Progress and Prospect of Li-Se Batteries: A Comprehensive Review,” Energy Materials 3 (2023): 300027.

[4] Z. Zhao, D. Chen, M. Lu, et al., “Single-Piece Membrane Supercapacitor With Exceptional Areal/Volumetric Capacitance via Double-Face Print of Electrode/Electrolyte Active Ink,” Small Methods 7 (2023): 2300178.

[5] X. Hu, Y. Zhang, J. Zhang, et al., “Sonochemically-Coated Transparent Wood With ZnO: Passive Radiative Cooling Materials for Energy Saving Applications,” Renewable Energy 193 (2022): 398–406.

[6] S. Kim, W. Shang, S. Moon, T. Pastega, E. Lee, and T. Luo, “High-Performance Transparent Radiative Cooler Designed by Quantum Computing,” ACS Energy Letters 7 (2022): 4134–4141.

[7] C. Zhou, I. Julianri, S. Wang, S. H. Chan, M. Li, and Y. Long, “Transparent Bamboo With High Radiative Cooling Targeting Energy Savings,” ACS Materials Letters 3 (2021): 883–888.

[8] M. Lian, W. Ding, S. Liu, et al., “Highly Porous Yet Transparent Mechanically Flexible Aerogels Realizing Solar-Thermal Regulatory Cooling,” Nano-Micro Letters 16 (2024): 131.

[9] M. Lee, G. Kim, Y. Jung, et al., “Photonic Structures in Radiative Cooling,” Light, Science & Applications 12 (2023): 134.

[10] T. Yu, R. Liu, Z. Yang, S. Yang, Z. Ye, and J. Lu, “Color Design for Daytime Radiative Cooling: Fundamentals and Approaches,” Applied Energy 377 (2025): 124436.

[11] R. Shanker, P. Ravi Anusuyadevi, S. Gamage, et al., “Structurally Colored Cellulose Nanocrystal Films as Transreflective Radiative Coolers,” ACS Nano 16 (2022): 10156–10162.

[12] Y. D. Lu, J. G. Lü, R. Q. Yang, B. J. Lu, L. P. Zhu, and Z. Z. Ye, “Transparent Conductive ZnO:Al/Cu Mesh Composite Film and Its Electric Heating Performance,” Acta Physica Sinica 71 (2022): 187304.

[13] K. Lin, S. Chen, Y. Zeng, et al., “Hierarchically Structured Passive Radiative Cooling Ceramic With High Solar Reflectivity,” Science 382 (2023): 691–697.

[14] K. Sun, W. Xiao, C. Wheeler, et al., “VO₂ Metasurface Smart Thermal Emitter With High Visual Transparency for Passive Radiative Cooling Regulation in Space and Terrestrial Applications,” Nanophotonics 11 (2022): 4101–4114.

[15] B. Zhao, M. Hu, X. Ao, N. Chen, and G. Pei, “Radiative Cooling: A Review of Fundamentals, Materials, Applications, and Prospects,” Applied Energy 236 (2019): 489–513.

[16] X. Yin, R. Yang, G. Tan, and S. Fan, “Terrestrial Radiative Cooling: Using the Cold Universe as a Renewable and Sustainable Energy Source,” Science 370 (2020): 786–791.

[17] D. Zhao, A. Aili, Y. Zhai, et al., “Radiative Sky Cooling: Fundamental Principles, Materials, and Applications,” Applied Physics Reviews 6 (2019): 021306.

[18] L. Zhou, J. Rada, H. Zhang, et al., “Sustainable and Inexpensive Polydimethylsiloxane Sponges for Daytime Radiative Cooling,” Advanced Science 8 (2021): 2102502.

[19] J. Mandal, Y. Fu, A. C. Overvig, et al., “Hierarchically Porous Polymer Coatings for Highly Efficient Passive Daytime Radiative Cooling,” Science 362 (2018): 315–319.

[20] R. Liu, K. Xia, T. Yu, et al., “Multifunctional Smart Fabrics With Integration of Self-Cleaning, Energy Harvesting, and Thermal Management Properties,” ACS Nano 18 (2024): 31085–31097.

[21] Z. Huang and X. Ruan, “Nanoparticle Embedded Double-Layer Coating for Daytime Radiative Cooling,” International Journal of Heat and Mass Transfer 104 (2017): 890–896.

[22] L. Cai, A. Y. Song, W. Li, et al., “Spectrally Selective Nanocomposite Textile for Outdoor Personal Cooling,” Advanced Materials 30 (2018): 1802152.

[23] J. Huang, M. Li, and D. Fan, “Core-Shell Particles for Devising High-Performance Full-Day Radiative Cooling Paint,” Applied Materials Today 25 (2021): 101209.

[24] X. Wang, X. Liu, Z. Li, et al., “Scalable Flexible Hybrid Membranes With Photonic Structures for Daytime Radiative Cooling,” Advanced Functional Materials 30 (2020): 1907562.

[25] J. Lv, Z. Chen, and X. Li, “Calcium Phosphate Paints for Full-Daytime Subambient Radiative Cooling,” ACS Applied Energy Materials 5 (2022): 4117–4124.

[26] A. P. Raman, M. A. Anoma, L. Zhu, E. Rephaeli, and S. Fan, “Passive Radiative Cooling Below Ambient Air Temperature Under Direct Sunlight,” Nature 515 (2014): 540–544.

[27] D. Chae, M. Kim, P.-H. Jung, et al., “Spectrally Selective Inorganic-Based Multilayer Emitter for Daytime Radiative Cooling,” ACS Applied Materials & Interfaces 12 (2020): 8073–8081.

[28] G. Huang, A. R. Yengannagari, K. Matsumori, et al., “Radiative Cooling and Indoor Light Management Enabled by a Transparent and Self-Cleaning Polymer-Based Metamaterial,” Nature Communications 15 (2024): 3798.

[29] Z. Wen, J. Tang, M. Zhai, et al., “Tough and Transparent Supramolecular Cross-Linked Co-Assembled Silk Fibroin Films for Passive Radiative Cooling,” Advanced Functional Materials 34 (2024): 2406920.

[30] G. Chen, Y. Wang, J. Qiu, et al., “A Visibly Transparent Radiative Cooling Film With Self-Cleaning Function Produced by Solution Processing,” Journal of Materials Science & Technology 90 (2021): 76–84.

[31] X. Zhang, X. Li, F. Wang, et al., “Low-Cost and Large-Scale Producible Biomimetic Radiative Cooling Glass With Multiband Radiative Regulation Performance,” Advanced Optical Materials 10 (2022): 2202031.

[32] K. W. Lee, J. Yi, M. K. Kim, and D. R. Kim, “Transparent Radiative Cooling Cover Window for Flexible and Foldable Electronic Displays,” Nature Communications 15 (2024): 4443.

[33] J. A. Spencer, A. L. Mock, A. G. Jacobs, M. Schubert, Y. Zhang, and M. J. Tadjer, “A Review of Band Structure and Material Properties of Transparent Conducting and Semiconducting Oxides: Ga₂O₃, Al₂O₃, In₂O₃, ZnO, SnO₂, CdO, NiO, CuO, and Sc₂O₃,” Applied Physics Reviews 9 (2022): 011315.

[34] L. Hu, C. Wang, H. Zhu, et al., “Adaptive Thermal Management Radiative Cooling Smart Window With Perfect Near-Infrared Shielding,” Small 20 (2024): 2306823.

[35] S. Wang, T. Jiang, Y. Meng, R. Yang, G. Tan, and Y. Long, “Scalable Thermochromic Smart Windows With Passive Radiative Cooling Regulation,” Science 374 (2021): 1501–1504.

[36] Y. Wu, Y. Chen, Q. Song, and S. Xiao, “Dynamic Structural Colors Based on All-Dielectric Mie Resonators,” Advanced Optical Materials 9 (2021): 2002126.

[37] D. Li, X. Liu, W. Li, et al., “Scalable and Hierarchically Designed Polymer Film as a Selective Thermal Emitter for High-Performance All-Day Radiative Cooling,” Nature Nanotechnology 16 (2021): 153–158.

[38] J. Huang, C. Lin, Y. Li, and B. Huang, “Effects of Humidity, Aerosol, and Cloud on Subambient Radiative Cooling,” International Journal of Heat and Mass Transfer 186 (2022): 122438.

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