image: Fig. 1 Machine learning inverse designed hybrid dielectric metasurface thermal emitter.
Credit: OEA
A new publication from Opto-Electronic Advances; DOI 10.29026/oea.2024.230194, discusses intelligent metasurfaces enable ultra-high performance passive radiative cooling.
Daytime passive radiative cooling is a recently demonstrated disruptive technology that could potentially transform the global energy landscape because of its zero-energy consumption and zero-carbon emission. The success of this technology replies on the spectral control over both the solar and thermal wavelengths by advanced photonic structures and micro/nano-fabrication technologies that enable simultaneous reflection of strong solar irradiation and radiation of heat to the ultracold outer space through the atmospheric transparency window.
The past decade has witnessed many photonic structure designs for achieving selective thermal emission spectra that match the atmospheric transparency window, including multilayer dielectric thin films, silica sphere/polymer metamaterials, plasmonic metasurfaces/nanoparticle. However, the emission profiles of these structures are still highly dispersive with either low emissivity or mismatched with the transparency window. In addition, real-world applications of radiative coolers exchange significant heat with surrounding environment through the non-radiative heat conductive and convection processes, imparting different constraints on the angular emission profiles.
The authors of this article propose machine learning inverse designed hybrid metasurface thermal emitters consisting of polar dielectric materials for highly selective, strongly emissive, and omnidirectional thermal emission (Fig. 1). By designing and optimizing the geometry-dependent multiple Mie resonances in the hybrid polar dielectric resonators, the group demonstrated thermal emitters with an emissivity of ~0.92 across the atmospheric transparency window, ultra-high spectral selectivity of ~1.8 and emission angle up to 80 degrees simultaneously, leading to a new record of equilibrium temperature reduction as large as ~15.4 ℃ in rooftop test (Fig. 2), significantly surpassing the state-of-the-art radiative coolers under non-vacuum conditions. The demonstrated radiative cooler also holds great promise for the urban heat island effect mitigation with modeling results suggesting a more than 50% deployment area reduction compared with the current radiative coolers.
Article reference: Zhang YN, Chen YG, Wang T et al. Ultrahigh performance passive radiative cooling by hybrid polar dielectric metasurface thermal emitters. Opto-Electron Adv 7, 230194 (2024). doi: 10.29026/oea.2024.230194
Keywords: halide perovskite / light-emitting-diodes / polarized emission / nanocrystals / stability
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Professor Min Gu is the Executive Chancellor of the University Council and Distinguished Professor of University of Shanghai for Science and Technology. He was Distinguished Professor and Associate Deputy Vice-Chancellor at RMIT University, and a Laureate Fellow of the Australian Research Council, Pro Vice-Chancellor, and a University Distinguished Professor at Swinburne University of Technology. He is an author of four standard reference books and has over 550 publications in nano/biophotonics. He is an elected Fellow of the Australian Academy of Science and the Australian Academy of Technological Sciences and Engineering as well as Foreign Fellow of the Chinese Academy of Engineering. He is also an elected fellow of the AIP, the Optica, formerly OSA, the SPIE, the InstP, the IEEE and the COS. He was President of the International Society of Optics within Life Sciences, Vice President of the Board of the International Commission for Optics (ICO) (Chair of the ICO Prize Committee) and a Director of the Board of the Optical Society of America (Chair of the International Council). He was awarded the Einstein Professorship, the W. H. (Beattie) Steel Medal, the Ian Wark Medal, the Boas Medal and the Victoria Prize for Science and Innovation. Professor Gu is a winner of the 2019 Dennis Gabor Award of SPIE and a winner of the 2022 Emmett Norman Leith Medal of OPTICA.
Prof. Yinan Zhang is the Assistant Director of Institute of Photonic Chips, University of Shanghai for Science and Technology. He received a bachelor's degree from Nankai University and a PhD from Swinburne University of Technology, Australia. His research mainly focuses on Nanophotonics, Optical Artificial Intelligence and Energy Photonics. He has published more than 30 highly prestigious journal papers. He was awarded the 2019 "Rising stars of Light" nomination prize, and the Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, China.
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