Flexible composite film with artificial opal photonic crystals for efficient all-day passive radiative cooling

Abstract

All-day passive radiative cooling has recently attracted broader attention for its potential as a viable energy technology. Although tremendous progress has been achieved, the design and fabrication of low-cost high-efficiency radiators for all-day passive radiative cooling remains a challenge. Herein, we report a new type of flexible composite radiator film with built-in artificial opal-like structures for all-day passive radiative cooling. Using artificial opal structure concepts, the proposed polydimethylsiloxane (PDMS) radiator film with embedded polystyrene (PS) microsphere photonic crystals exhibits a sufficiently high solar reflectance of ∼92.7% when in a direct sunlight region, and a thermal emittance of ∼93.6% within the atmospheric window. Without the need for traditional reflectors like silver or aluminum foils, this composite film realizes subambient temperature reduction of ∼4.8 °C in direct sunlight and ∼8.5 °C during the night. This work provides a new fabrication approach for the low-cost production of structural polymer films for high performance and potential real word applications.

Flexible Photonic Radiative Cooling Films: Fundamentals, Fabrication and Applications

“…Recently, Nan et al reported a polydimethylsiloxane (PDMS) radiator film with embedded polystyrene (PS) microsphere photonic crystals (Figure 6e). [103] By manipulating the diameter of the microspheres, the opal-like structure achieves low absorptance of solar energy. The inner PS microsphere arrays stimulate optical resonance in sphere-tosphere, sphere-to-layer, and layer-to-layer (Figure 6f).…”

“…We compare a variety of typical designs that possess sufficient daytime radiative cooling capabilities (Table 1). [12,15,16,[20][21][22]77,[91][92][93][94][95][97][98][99][101][102][103][104]108,[111][112][113] As evidenced by empirical evidence, these cooling apparatuses exhibit unprecedented cooling efficiency, with a magnitude of 61 to 163.9 W m −2 and an attendant decrease in temperature ranging from 1.88 °C to 13.8 °C. It is noteworthy that the superlative performance of radiative cooling is commonly contingent upon a manifold of photon mechanisms that coalesce to bring about an efficacious outcome.…”

“…e,f) Reproduced with permission. [ 103 ] Copyright 2022, The Optical Society. g–i) Reproduced with permission.…”

“…Copyright 2021, The Authors, published by Springer Nature. e,f) Reproduced with permission [103]. Copyright 2022, The Optical Society.…”

Bioinspired Design of a Binary Synergistic Photonic Structure for Daytime Radiative Cooling

“…18,19 Among these, photonic structures exhibit tailored spectrum via tuning the subwavelength structural features, realizing distinctive radiative cooling performance. 20,21 Strategies for constructing photonic structures like multilayer stacks, 22 periodic structures, 23 random structures, 24 and bioinspired structures 25 thrive in achieving highly efficient passive radiative cooler. 26 Raman et al 27 first reported a multilayer photonic structure used for radiative cooling with a solar reflectance of 97% and selective emissivity across the atmospheric transparency window.…”