achieve this efficiency due to its dependency on the operating temperature. It is stated that the high efficiency in various SCs can be achieved at an illumination of AM 1.5G and a temperature of 25 °C. However, the temperature of the SC typically exceeds this value in outdoor conditions, where it heats up by tens of degrees above the ambient temperature, which decreases the lifespan and efficiency of the SC. [14,15] The passive radiative cooling method can potentially resolve the heating issue of the SC owing to its compact and costeffective approach. It involves spontaneously cooling objects by emitting heat to the outer space without consuming energy through the transparent atmospheric transmittance window (λ ≈ 8-13 µm). [16][17][18] Recent studies have presented various types of radiative coolers (RCs) [19][20][21][22][23][24][25][26][27] which have been demonstrated to successfully lower the temperature of SCs. [28][29][30] Research has also been conducted to theoretically analyze the effectiveness of RCs in compensating for the reduced conversion efficiency of SCs due to elevated temperatures. [31][32][33][34] However, these studies have evaluated or tested the potential of an RC on specific target SCs, such as silicon, [35][36][37][38][39] concentrated perovskite, [40][41][42][43] or low-bandgap concentrated perovskite, [41] which are limited to single-junction SCs. Further research is required to determine the type of SC that can most retain its original efficiency even at high environmental temperatures, when adapting the RC technique.The efficiency of SCs can be significantly improved through a comprehensive understanding of the practical operation of the RC on diverse SCs since the SC industry encompasses various types of cells. This study theoretically proves that the multi-junction SC (MJSC) is the most effective type of SC when an RC is applied. It also presents the limitations of the radiative cooling technique when sub-bandgap (sub-BG) absorption is considered. Consequently, the proposed MJSC is demonstrated to be immune to heating by sub-BG photons, which can lead to the development of novel SCs by reducing the burden of designing additional sub-BG filters [44] or reflectors. [45][46][47] A structure is then fabricated which performs both light trapping and radiative cooling based on pioneering SC research, and is applied to the InGaP/GaAs/Ge MJSC. Multiple outdoor experiments are conducted to demonstrate that radiative cooling can contribute to a temperature drop of ≈6 °C. The reduced temperature also results in an absolute increase of the open-circuitThe power-conversion efficiency of solar cells (SCs) is reduced at high temperatures. A radiative cooling process can be implemented to overcome this issue. The radiative cooler (RC) presents considerable potential in the design of an ideal broadband emitter, which emits heat through the entire atmospheric transmittance window for devices with operating temperatures that significantly exceed the ambient temperature. However, the performance of thes...
Reconfigurability of a device that allows tuning of its shape and stiffness is utilized for personal electronics to provide an optimal mechanical interface for an intended purpose. Recent approaches in developing such transformative electronic systems (TES) involved the use of gallium liquid metal, which can change its liquid-solid phase by temperature to facilitate stiffness control of the device. However, the current design cannot withstand excessive heat during outdoor applications, leading to undesired softening of the device when the rigid mode of operation is favored. Here, a gallium-based TES integrated with a flexible and stretchable radiative cooler is presented, which offers zero-power thermal management for reliable rigid mode operation in the hot outdoors. The radiative cooler can both effectively reflect the heat transfer from the sun and emit thermal energy. It, therefore, allows a TES-in-the-air to maintain its temperature below the melting point of gallium (29.8 °C) under hot weather with strong sun exposure, thus preventing unwanted softening of the device. Comprehensive studies on optical, thermal, and mechanical characteristics of radiative-cooler-integrated TES, along with a proof-of-concept demonstration in the hot outdoors verify the reliability of this design approach, suggesting the possibility of expanding the use of TES in various environments.
Radiative cooling, which is based on radiative heat exchange between the universe and Earth, can provide a passive and renewable route to reducing energy consumption. Radiative cooling was historically limited...
Recent advances in passive radiative cooling systems describe a variety of strategies to enhance cooling efficiency, while the integration of such technology with a bioinspired design using biodegradable materials can offer a research opportunity to generate energy in a sustainable manner, favorable for the temperature/climate system of the planet. Here, we introduce stretchable and ecoresorbable radiative cooling/heating systems engineered with zebra stripe–like patterns that enable the generation of a large in-plane temperature gradient for thermoelectric generation. A comprehensive study of materials with theoretical evaluations validates the ability to accomplish the target performances even under external mechanical strains, while all systems eventually disappear under physiological conditions. Use of the zebra print for selective radiative heating demonstrates an unexpected level of temperature difference compared to use of radiative cooling emitters alone, which enables producing energy through resorbable silicon-based thermoelectric devices. The overall result suggests the potential of scalable, ecofriendly renewable energy systems.
Optimized thermal emitters using optical resonances have been attracting increased attention for diverse applications, such as infrared (IR) sensing, thermal imaging, gas sensing, thermophotovoltaics, thermal camouflage, and radiative cooling. Depending on the applications, the recently developed IR devices have been tailored to achieve not only spectrally engineered emission but also spatially resolved emission using various nanometallic structures, metamaterials, and multistacking layers, which accompany high structural complexity and prohibitive production cost. Herein, this article presents a simple and affordable approach to obtain spatially and spectrally selective hybrid thermal emitters (HTEs) based on spoof surface plasmons of microscaled Ag grooves manifested in encapsulation polymer layers. Theoretical analyses found that the polymer hybrid plasmonics allows diverse emission tuning within the long-wave IR (LWIR; 8–14 μm) region as follows: (1) spatially selective emission peaks only exist in the interface of Ag grooves and IR-transparent layers and (2) near-unity spectrally selective emission is obtained by refining inherent emissivity of a thin IR-opaque layer. Also, parametric studies computationally optimized the structural parameters for spatially and spectrally selective HTEs. Using the optimized parameters, the authors fabricated two HTEs and demonstrated the intriguing emission features in terms of infrared data encoding/decoding and radiative cooling, respectively. These successful demonstrations open up the applicability of HTEs for tailoring IR emission in a spatially and spectrally selective manner.
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