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13 August 2020 Recent advances and progresses in photonic devices for passive radiative cooling application: a review
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Abstract

This review covers the recent progress made in the nanophotonic devices-based daytime passive radiative coolers. The radiative cooling capabilities along with the structural description of various natural species are discussed. The design principle along with key characteristics of the omnidirectional solar reflectors as well as thermal adiators is discussed in detail. Several analogues planner one-dimensional and two-dimensional photonic nanostructures and their current state-of-the-art techniques have been discussed. For each kind of the photonic structure, the novelty, measurement principle, and their respective daytime radiative cooling capability are presented. The reported works and the corresponding results predict the possibility to realize an efficient and commercially viable radiator for passive radiative cooling applications.

1.

Introduction

Cooling represents a significant sector of energy consumption.1 It is the most significant driver of peak electricity demand as well as considerable end use of energy globally.2 The global energy consumption can be reduced by adopting a cooling strategy that can cool without any electrical input, which is also known as passive cooling technique. The cooling can be achieved if one is able to reach and maintain a temperature below ambient temperature. Radiative cooling, as a passive radiative cooling scheme, does not require any external active devices, such as fans, air conditioners, or thermoelectric.35 It works on the principle that the atmosphere is almost transparent between 8 and 13  μm (also known as ‘‘sky window”). Thus, utilizing outer space as a heat sink by allowing the emission of thermal radiation from surface to the universe.6,7

In the past few decades, the radiative cooling strategy has been widely explored. Its significance along with potential application in cooling during nighttime was practically demonstrated.810 A number of different materials showing the capability of intrinsic infrared (IR) emissions for substantial radiative cooling have also been explored previously.1113 These results well demonstrate the capability of the radiative cooling technique. However, the work was mostly limited for the nighttime radiative cooling only. This is because of the availability of suitable materials that possess good IR emission within the atmospheric window. But the primary cooling power requirement usually occurs during the presence of the sun (daytime as compared to nighttime).14 The presence of Sun also affects the radiator’s efficiency. Therefore, for daytime cooling, both high emissivity (in sky window) and high reflectivity (of the complete solar spectrum) are required. This approach utilizes the universe as a heat sink to release the heat through the atmospheric window and minimize the absorption of incoming atmospheric radiation. Then the surface temperature can be decreased below the ambient. Therefore, certain natural materials, such as polymeric materials,15,16 titanium dioxide,1719 silicon nitrides,20 and silicon-monoxide (SiO),21 have potential for limited selectivity. But it is difficult to find out a simple bulk material with high emissivity and high reflectivity in the desirable spectrum range simultaneously.22 However, many natural species possess the capability to cool down themselves by exhibiting both the aforementioned properties simultaneously. Inspired from natural species, a lot of work is also carried out to design nanophotonic devices for daytime radiative cooling applications. This facilitates capacity to simultaneously possess a reflectivity of more than 97% for complete solar spectrum and strong IR emission within the sky window.2326 The development of nanophotonics structures is certainly an important factor that helps in the current resurrection of passive radiative cooling techniques.

Interestingly, one recent article demonstrated the potential of one-dimensional photonic crystal (1D-PhC) structure that can cool down an entity below the ambient temperature using the same technique to that of Sahara silver ants, i.e., highly reflective and emissive for the desirable spectrum range.27 Similarly, another recent report has also been reported for this purpose by mimicking the structural attributes of Morpho butterfly wings and successfully demonstrated the passive radiative cooling strategy.28 These emerging nanophotonic devices can offer an efficient cooling strategy with their strictly selective and achievable properties and have triggered significant research interest in this area.

Within this context, this review provides sufficient details regarding design principle, radiative cooling characteristics, and recent progress made toward the development of daytime passive radiative cooling devices. Section 2 presents an overview of biomimetic analogy of radiative cooling and motivation behind developing these devices. Section 3 presents a detail working principle of radiative cooling. The approach for nighttime and daytime applications is identified. This section also discusses the design strategy for omnidirectional reflector (ODR). In Sec. 4, we review the different material systems along with various 1D and 2D nanophotonic devices developed for daytime passive radiative cooling applications in the earlier studies. Their working principles and performances of the reported designs are thoroughly investigated and possible efficiency improvement strategies are discussed. Section 5 discusses the current challenges and scopes of daytime passive radiative cooling technique and finally Sec. 6 concludes the review.

2.

Radiative Cooling’s Biomimetic Analogy

While the proposed passive daytime radiative cooling concept is potentially transformative for metallic structures, the idea of selective passive radiative cooling is not new to nature. Various insects and animals living in hot environment, such as Morpho butterfly, Pompeii worm (Alvinella pompejana), Sahara Desert ant (Cataglyphis bicolor), and water bear or Tardigrade (Hypsibius dujardini) possess the capability to withstand extreme climate changes. For example, Pompeii worm and Sahara Desert ant can withstand a temperature as high as 176°F (80°C) and 122°F (50°C), respectively.29,30 Water bear is capable of surviving the temperature more than 302°F (150°C).31 This happens only because of their unique body structure that helps them to overcome the heating challenges. Alongside, beetles (Coleoptera) exhibit a number of interesting optical phenomena, i.e., metallic colors and spectral iridescence.32 Recently, the white structure presents on beetles’ elytra has also attracted researchers’ interest to explore this mechanism. Many authors have further explored the optical functionalities of these species to develop various new biological photonic structures.3336

If an entity keeps on absorbing the significant portion of solar radiation, it will not survive. Therefore, most of the natural substances have their body structures that help them to reflect solar radiation. For example, Morpho butterfly has empty pores within the thin membranes, which helps them to scatter near-IR radiation and avoid excessive heating under sunlight.37 The Morpho butterfly image and corresponding pictorial representation of internal structure are shown in Figs. 1(a) and 1(b), respectively. Furthermore, these species also exhibit strong emissive properties in mid-infrared (MIR) range, thereby using universe as heat sink as explained earlier.28,38 Similarly, the internal structure of Bistonina biston butterfly’s wings also exhibits spectrally selective emissivity values. This helps butterfly to cooldown the wing surface. Because of its unique structure, it exhibits a high emissivity in the MIR (2.5 to 16  μm) to dissipate heat and it is highly reflective to the solar spectrum, which helps it to cool the wings.39

Fig. 1

(a) The Morpho didius butterfly image (image source: wiki image) and (b) schematic of corresponding internal structure.

JNP_14_3_030901_f001.png

Saharan silver ant is another widely studied insect that possesses the capability to stay cool in the Saharan Desert under the direct sunlight. The amazing temperature management ability of Saharan silver ants is also due to their unique structural geometry. The Saharan ants are covered with a dense array of hairs with triangular shapes on both the top and sides of their bodies as shown in Fig. 2.27,40 It has been recently demonstrated that the periodical arrangement of their hair structures makes them reflective to the solar spectrum (0.4 to 1.7  μm) and highly emissive in the MIR range (2.5 to 16  μm).27 These uniquely shaped silvery hairs protect and enable the ants to maintain lower body temperatures by two main mechanisms (i.e., reflection of most of the solar spectrum and transferring heat to the universe by improving the emissivity in the MIR region) similar to the Bistonina biston butterfly. The combined effect helps the silver ant to maintain steady-state body temperature.

Fig. 2

The Sahara silver ant structure. (a) Scanning electron microscopy (SEM) image of ant’s head covered with hairs. (b) SEM image of ant’s abdomen covered with hairs. (c) and (d) The close-up look via SEM imaging (Copyright 2016 Willot et al.40).

JNP_14_3_030901_f002.png

Another example present in nature is the cocoon made by wild silk moths. The cocoons comprise a number of fibers arranged randomly and scatter the incident light. This attributes to high solar reflectivity along with high MIR emissivity.41,42 This helps moth pupae from overheating under the direct sun. In 2018, Choi et al.43 explored the internal structure of silkworm fibers and found the presence of microcavities. These microcavities are responsible for both reflections of the solar spectrum and suppression of the transmission spectrum via Anderson localization.

The thermoregulatory solutions demonstrated by natural species are the examples that show the capability of an animal to control electromagnetic waves over an extremely broad range of the spectrum (almost complete solar spectrum). These remarkable effects observed in these natural species could be very interesting and have a massive technological impact and inspiration for the development of nanophotonic devices for passive radiative cooling applications.

3.

Fundamental Principles of Passive Radiative Cooling

3.1.

Design Principle of Passive Radiative Cooler

In this section, the fundamental principle behind the passive radiative cooling strategy is presented. The environmental radiations comprise both solar radiation and emitted IR radiation from the Earth’s surface, which is further used to maintain the energy balance.44 This energy balance is required to maintain an equilibrium temperature. When a surface under consideration is exposed to the environment, the cooling power Pcool is considered to be the resultant out-going radiative energy flux and can be represented by

Eq. (1)

Pcool(T)=Prad(T)Patm(Tamb),
where Prad(T) and Patm(Tamb) are the thermal emission of the radiative cooler and thermal atmospheric radiations with the operating temperature T and Tamb, respectively. These can be calculated by

Eq. (2)

Prad(T)=AdΩcosθ0dλIB(T,λ)ε(λ,θ),

Eq. (3)

Patm(Tamb)=AdΩcosθ0dλIB(Tamb,λ)ε(λ,θ)εatm(λ,θ),
where εatm represents the spectral and angular atmospheric emittance. The lowest achievable temperature directly depends on the net cooling power. Higher net cooling power leads to attaining the lowest temperature. This also depends on various other factors such as incident solar power and conductive heat transfer during daytime. Thereby, a passive radiative cooler is a structure that can provide temperature lower than that of ambient air. For a surface that is directly exposed to the atmosphere under sunlight (as shown in Fig. 3), the net radiative cooling power can be obtained by modifying Eq. (1) and represented by following equations:45

Eq. (4)

Pnetrad=PradPatmPsolar,

Eq. (5)

Pnet=PradPatmPsolarPnonradiative,
where Prad is the thermal emission of the radiative cooler (surface), Patm is the absorbed atmospheric radiation power on the surface, and Psolar is the absorbed incident solar radiation power on the surface. It is noteworthy to mention that Eq. (4) represents the net radiative cooling of a surface by considering the effect of only atmospheric and solar radiations. The structure under consideration is directly exposed under the sunlight. To consider other surrounding effects or nonradiative heat exchange process, Eq. (4) can be modified as Eq. (5).

Fig. 3

Schematic structure of the heat transfer on a surface under consideration.

JNP_14_3_030901_f003.png

Figure 3 represents the pictorial working principle of daytime passive radiative cooling devices, where the mentioned terminologies are already explained earlier. According to Eq. (5), Psolar and Pnonradiative behave as parasitic cooling losses those attribute to the reduction in the overall cooling efficiency. This further leads to increase in the cooling time to obtain the thermal equilibrium. In addition, the cooling efficiency also depends on the emission characteristic of the radiator, i.e., broadband or selective radiator. The ideal broadband radiator possesses the capability with unity emittance throughout the IR spectrum along with negligible absorption for the complete solar spectrum in daytime radiative cooling applications. Spectrally selective cooler possesses the unity emittance only in the atmospheric window.46

The structural net radiative cooling efficiency or cooling time can be improved by minimizing the absorption of atmospheric and solar radiation. Generally, the radiation property of a perfect absorber (blackbody) is also very strong and research is being carried out to design perfect absorber.47,48 The solar radiations are considered to be equivalent to that of a blackbody radiations for an effective temperature of around 5800 K. Figure 4(a) represents the normalized atmospheric transmission for different wavelengths, where it appears to be highly transparent from 8 to 13  μm. One more sky window also appears between 16 and 23  μm. Due to its weak transmittance, it has very less significance for radiative cooling and neglected in general. The Earth’s atmosphere exhibits good emissivity outside this window. Coincidentally, the peak thermal radiation characteristic of a blackbody (at around 300 K) overlaps with the atmospheric window, as shown in Fig. 4(a). The emitted IR rays pass through the Earth’s atmosphere and move into the outer space. Thereby, it uses universe as a heat sink. Figure 4(b) shows the spectral irradiance graph of AM 1.5 solar spectrum (at irradiance of about 1000  Wm2). The absorption of this power can drastically affect the cooling performance of the radiator. Apart from these, atmospheric conditions also affect the performance of daytime radiative cooling structures. This has already been discussed in various earlier reports.4952 To minimize the effects of incoming solar radiation, an IR transparent reflector needs to be integrated on the top side of the surface. Alternatively, a cooling device itself can be designed that possesses the capability to serve as both solar reflector and IR radiator simultaneously.

Fig. 4

(a) The effect of wavelength on atmospheric transmittance and spectral irradiation (reprinted from Zhao et al.,6 with the permission from AIP) with the comparison of blackbody radiations. (b) The spectral irradiance graph of AM 1.5 solar spectrum (data from Ref. 136).

JNP_14_3_030901_f004.png

3.2.

Design Principle of Dielectric Reflectors

The dielectric reflector is a structure that possesses the capability to reflect the complete solar spectrum at all incident angles. This is also considered as omnidirectional broadband reflector. The structure works on the principle of distributed Bragg reflector (DBR), where optical length optimization is carried out to enhance the reflectivity. Optical length can be varied by changing layer properties, such as height, RI, and porosity. Each layer causes a partial reflection of incident radiation as shown in Fig. 5. In Fig. 5(a), layer “A” corresponds to the material of high RI and layer “B” is of low RI. The structure is designed in such a way that all the reflected waves constructively interfere to give an overall high reflection. This constructive interference condition can easily be governed by Bragg’s law as shown in Fig. 5(b).

Fig. 5

Schematic diagram of (a) DBR structure and (b) Bragg’s law.

JNP_14_3_030901_f005.png

The structure can be designed using a quarter-wavelength Bragg reflector. The analysis can be carried out by considering a material system of high and low refractive indices that should also have high emissivity in the atmospheric window. Generally, the structure is designed to reflect a broadband spectrum centered at wavelength (λ0). For normal incident, the layer thicknesses are obtained using Eqs. (6) and (7), while Eq. (8) is used for oblique incident.

Eq. (6)

nHdH=mλ04,

Eq. (7)

nLdL=mλ04,

Eq. (8)

λ02=dLnL2sinθ2+dHnH2sinθ2,
where nH and dH are the RI and thickness of high refractive index material, respectively, nL and dL are the RI and thickness of low refractive index materials, respectively, θ is the incident angle, and λ0 is the center reflected wavelength. The width of reflection spectrum depends on various parameters, such as index contrast between layers and number of bilayers. However, one needs to overcome the trade-off between high reflectivity and high full-width-half-maximum. Theoretically, the structure can be designed and optimized by following various classical optimization methods, such as needle optimization,53,54 simulated annealing,55 jump method,56 and memetic algorithm.57

4.

Recent Progress and Discussions

Achieving subambient radiative cooling during nighttime is straightforward. But, in the daytime, the presence of the sun creates the difference. The cooling scenario can further be divided into four major parts, i.e., daytime above-ambient and subambient, nighttime above-ambient and subambient as shown in Fig. 6. Most of the radiators are designed to exhibit the characteristic similar to these ideal emissivity/absorptivity spectral curves. For nighttime cooling, 2.5- to 50-μm wavelength range is of interest. For daytime, it is of around 0.3 to 50  μm (i.e., extra 0.3 to 2.5  μm is because of solar spectrum).

Fig. 6

The emissivity and absorptivity spectrum for various cooling scenarios, daytime above-ambient (solid black line), daytime subambient (red dashed line), nighttime above-ambient (orange dashed line), and nighttime subambient (solid blue line), respectively (reprinted from Zhao et al.,6 with permission from AIP).

JNP_14_3_030901_f006.png

Subambient daytime cooling applications require the emissivity equivalent to blackbody emissivity in the atmospheric window and emissivity close to zero in the solar spectrum. This radiator has to be selective as explained in Sec. 3. The major research works for nighttime subambient radiative cooling devices are based on developing structures for selective IR emission in the sky window that is represented by a solid blue line in Fig. 6.5861 However, for daytime cooling (either above-ambient or subambient) as shown by black solid and red dashed lines in Fig. 6, the major challenge is to achieve both high solar reflectance and high emissivity over the atmospheric window. A lot of research studies have been carried out to design structures that can reflect complete solar spectrum as well as are highly emissive in the atmospheric transparent window. The following section describes various strategies to design a broadband solar reflector followed by their applications in realizing daytime radiative cooling devices.

4.1.

Dielectric Omnidirectional Reflector

The recent progress on developing nanophotonic devices based on radiators for passive radiative cooling applications has provided a new direction toward achieving highly efficient devices. Thus, improving the ability to effectively work directly under the sun by maintaining their temperatures below the ambient. Photonic crystal (PhC)-based structures are extensively investigated because of their light controlling and bandgap properties.6267 These properties are further used to design various one-dimensional (1D) and two-dimensional (2D) PhC-based structures for passive radiative cooling applications.6871 The PhC structure shows a complete photonic bandgap (PBG), when no electromagnetic mode is allowed to propagate through the structure and behaves as a perfect reflector.72,73 The width of reflection spectrum (or PBG) is important while designing an ODR specifically, for applications such as daytime radiative cooling.74 To achieve daytime radiative cooling, an ODR is required that should have the capability to reflect complete solar spectrum for both TE and TM polarization.7577 The metallic reflectors are widely accepted for reflection purposes but their widespread uses are limited because of their lossy properties at optical wavelengths.78 Therefore, dielectric-based structures are considered to be good alternatives for this purpose as they also provide design flexibility in terms of reflection wavelength.79 Different types of 1D-PhC structures have already been investigated to design ODRs.

Fink et al.80 and Winn et al.81 presented a 1D-PhC-based dielectric structure with nine layers of an alternating stack of polystyrene/tellurium materials and reported an ODR over the wavelength range from 10 to 15  μm. The ODR bandgap can also be enlarged by considering heterojunction photonic multilayer structures.8284 Joseph et al.85 proposed a dispersive 1D-PhC structure made of SiO2 (as low-index medium) and GaSb (as high index medium) and reported an ODR in 1480- to 1680-nm wavelength range. The combination of dielectric and birefringent material has also been explored for designing of ODR structures. Upadhyay et al.86 used potassium titanyl phosphate (KTP)/lead sulfide (PBS) as birefringent materials and SiO2 as a dielectric material and reported an ODR over the wavelength range of 3.155 to 4.202  μm. The ODR bandgap was further enhanced by considering graded structures of same material and reported an ODR over a wavelength range of 3.188 to 4.655  μm.87

Various natural species (i.e., Papilio palinurus butterfly, silvery fish, etc.) have also been studied to understand their ODR phenomena. Jordan et al.88 and later Zhao et al.89 studied and reported a nonpolarizing optical mechanism found in the broadband guanine-cytoplasm “silver” multilayer reflectors of three species of fish. The silvery reflections from the fish are because of the multilayer stacks of guanine crystals and index cytoplasm.90,91 These work as high and low refractive index media, respectively. Similarly, Han et al.23 studied the Papilio palinurus butterfly structure and theoretically and experimentally reported the findings of novel omnidirectional reflective self-stable properties. Furthermore, based on this study, the authors successfully designed and fabricated a SiO2-material-based bioinspired color reflector using a simple biotemplate method. Although, the reported papers clearly demonstrate capability of dielectric-based 1D-PhC structure to design ODR but width of reflection spectrum is still a tricky task to cover complete solar spectrum. Table 1 summarizes the recent work done on designing ODRs.

Table 1

Summary of the recent development in ODR design.

StructureMaterialsODR range (μm)ODR width (μm)YearReferences
PlannerPolystyrene/tellurium10 to 1551998Fink et al.80
PlannerSiO2 and GaSb1.48 to 1.680.202014Joseph et al85
PlannerKTP/PBS as birefringent and SiO2 as dielectric3.155 to 4.2021.0472012Upadhyay et al.86
Graded3.188 to 4.6551.4672018Kumar et al.87
Decreasing width multilayerCsBr/Te12 to 20082017del Barco et al.137
MultistackingSiO2 and Si3N40.3 to 2.42.1 (TE only)2019Ratra et al.138
MultistackingSiO2 and Si3N40.3 to 2.32.02020Ratra et al.139
PlannerPorous silicon1.0 to 2.02.02020Castillo et al.140

4.2.

Radiative Coolers Based on 1D Nanophotonic Structure

Rephaeli et al.92 proposed a metal–dielectric-based multilayer structure with three sets of five bilayers of MgF2 and TiO2 materials as shown in Fig. 7(a). The proposed structure is embedded between two layers of 2D photonic crystal (2D-PhC) made of quartz and SiC and shows the omnidirectional reflectivity for complete solar spectrum. The proposed structure shows its capability of achieving a net cooling power of around 100  W/m2 at environmental temperature. Similarly, Raman et al.93 designed a structure with planar photonic device consisting of seven alternating layers of hafnium oxide (HfO2) and SiO2 (having different layer thicknesses) on a silver-coated silicon substrate as shown in Fig. 7(b). The bottom SiO2/HfO2-based thinner structure is responsible for solar reflection, while the top thicker structure is designed for thermal radiation. The authors experimentally reported a 97% reflection of the complete solar spectrum and an average emissivity of about 0.65 in the transparency window. They experimentally demonstrated a temperature reduction of 4.9°C below the ambient under direct sunlight. This structure has been widely studied by many researchers. Different materials are considered for further improvement in the net cooling power. Kecebas et al.94 replaced HfO2 with TiO2 material along with a top Al2O3 layer. Jeong et al.95 further optimized this TiO2SiO2-based daytime radiative cooler structure with an average emissivity of 0.84 in the sky window along with 94% reflectivity of incident solar energy as shown in Fig. 7(c). The authors estimated the net cooling power around 136.3  W/m2. This shows 90  W/m2 improvement in cooling power compared to that of the HfO2/SiO2 material-based photonic radiative cooler structure. The authors successfully demonstrated a reduction of 7.2°C in temperature along with a net cooling power of 14.3  W/m2 under direct sunlight using solar shading.

Fig. 7

Schematics of various 1D nanophotonic structures used for radiative cooling. Each design as a different layered structure: (a) MgF2TiO2-based structure,92 (b) HfO2SiO2 multilayer,93 (c) modified structure by replacing HfO2 with TiO2,95 (d) porous AAO membranes-based design,96 (e) Si3N4SiAl-based structure,97 and (f) PTFE and Ag on Si substrate.104

JNP_14_3_030901_f007.png

Fu et al.96 demonstrated a daytime passive radiative cooler composed of porous anodic aluminum oxide (AAO) membranes as shown in Fig. 7(d). The porosity (or air doping) and AAO thickness were optimized to get the desired results. The designed structure is capable of providing a power density of 64  W/m2 at environmental temperature (at humidity of 70%) under direct sunlight. The authors experimentally showed the structure cooling by reducing temperature by 2.6°C below the ambient air under direct sunlight. In another report, Chen et al.97 used silicon nitride (Si3N4), silicon (Si), and aluminum (Al) to design a multilayer structure [as shown in Fig. 7(e)] that works as an ideal selective thermal emitter for sky window. The authors reported an average 42°C temperature reduction below ambient.

Furthermore, calcium fluoride (CaF2) and germanium (Ge)-based material systems are also explored and used by Huang et al.98 Authors designed an “invisible” radiative cooling structure by considering a nichrome metal film on which seven alternating layers of CaF2/Ge were deposited. The structural parameters were optimized to get the desired results. To reduce the cost, polymer materials are also explored for this application. Polyvinyl fluoride, polyvinyl chloride, poly-dimethyl-siloxane (PDMS), polyethylene terephthalate, and polymethylpentene (TPX) are commonly used polymer materials, which are widely used for radiative cooling applications.99102 These materials are beneficial as they offer very strong IR emission and possess the capability of large-scale production along with the low cost.

However, polymer material-based radiators have various concerns that are discussed in detail in later sections. Gentle et al.103 used polymer materials to demonstrate reduction in temperature below ambient. The structure was designed by considering birefringent polymer materials arranged in stacked-like structure. Thus, creating a polymer-based reflector for the visible spectrum. To cover the complete solar spectrum, a silver metallic layer was deposited at the bottom side, which is used to reflect the IR wavelength range of the spectrum. Based on the structures, the authors successfully demonstrated cooling of 2°C below the environmental temperature under the direct sunlight with the irradiation of about 1060  Wm2. In 2017, a polymer-coated fused silica mirror was also proposed. The designed structure exhibits the characteristic of a near-ideal blackbody as well as near-ideal reflector in the MIR and in the solar spectrum, respectively. The authors demonstrated the radiative cooling below ambient air temperature during daytime (8.2°C) and during nighttime (8.4°C).26 Recently, Yang et al.104 used polytetrafluoroethylene (PTFE) and Ag film on Si substrate [as shown in Fig. 7(f)] and successfully demonstrated radiative cooling to 11°C below the environmental temperature.

The reported results demonstrated well the possibilities of 1D nanophotonic structures to control light in the multiple photonic bands (sky window and solar spectrum) that are extremely desirable for daytime passive radiative cooling applications. However, designing an ODR that can cover complete solar spectrum [ultraviolet (UV) to IR] using simple 1D photonic structures is difficult. Furthermore, the application of metal as back-reflector also affects the reflection of UV spectrum. This is because of the metallic absorption coefficient in the UV wavelength region.105 Working toward this goal, Yao et al.106 proposed a dual-band selective emitter with multinanolayers. Authors used a tandem SiO2/Si3N4 PhC-based structure with different PBGs (PhC1 and PhC2), which are stacked over a silver metallic reflector. The proposed design (as shown in Fig. 8) shows its capability of radiative cooling to 11°C below the environmental temperature under direct sunlight.

Fig. 8

Schematics of the proposed tandem PhC stack-based radiative cooling design.106

JNP_14_3_030901_f008.png

The average emissivity of the design can also be improved using colored radiative coolers. Compared to traditional radiative cooling structures, this technique leads to increase in overall emissivity within the sky window and leads to reduction in the cooling loss. Recently, Sheng et al.107 designed a colored radiative cooler structure based on optical Tamm resonance. The proposed structure possesses the capabilities to produce high-performance cooling and can retain high-purity subtractive primary colors (CMY). The authors used the Tamm structure, composed of a DBR (MgF2/SiC) on top of a silver film, and successfully presented a temperature reduction of 5°C to 6°C. Table 2 summarizes the recent work done on designing radiative cooler based on 1D nanophotonic structure.

Table 2

Summary of the recent development in 1D nanophotonic structures.

MaterialsCooling power (W/m2)Temperature reduction (°C)YearReferences
SiO2TiO2-based structure14.37.22020Jeong et al. 95
Porous AAO membranes on aluminum substrate642.62019Fu et al.96
PDMS film on a reflective metal substrate3.22019Zho et al.101
A 150-nm-thick silver (Ag) and 50-nm-thick SiO2 on a 500-μm-thick SiO2 substrate5.92019Zhao et al.141
Tandem SiO2/Si3N4112019Zho et al.101
MgF2/SiC multilayer on top of a Ag film5 to 62019Sheng et al.107
Structure made by ultrawhite glass-plated Ag2.52019Ao et al.142
Zinc phosphate sodium (NaZnPO4) particles on aluminum (Al) substrate1.52019
(PTFE) and Ag film on Si substrate112017Yang et al.104
Two layers of acrylic resin embedded with TiO2 and carbon black particles10062017Huang et al.76
Stack of PDMS/SiO2/Ag1278.22017Kou et al.26

4.3.

Radiative Coolers Based on 2D Nanophotonic Structures

Furthermore, 2D structures are also explored for designing daytime radiative coolers. Nanophotonic structures with structural dimensions around wavelength exhibit distinct radiation properties.108,109 Microresonator structures are excellent candidates to reflect or absorb a given wavelength.110112 A number of nanophotonic structures, such as conical pillar arrays, dielectric resonator metasurfaces, metal–dielectric–metal resonators, and multilayer pyramidal nanostructures, are explored to design daytime passive radiative coolers. These structures possess the capability to tailor the spectral selectivity of the surfaces. Initially, Rephaeli et al.92 explored the possibility of daytime radiative cooling using a nanophotonic structure and successfully demonstrated a temperature reduction of almost 4.9°C below the ambient.

A general strategy for achieving color-preserving radiative cooling using an α-quartz nanostructure has also been proposed.113 The structure comprises an array of α-quartz bars placed on top of another arrayed structure made of silicon bars [as shown in Fig. 9(a)]. The color-preserving radiative cooling strategy can also be implemented using a multilayer photonic radiator.114 Zhu et al.115 used a SiO2-based PhC absorber for radiative cooling applications. The oxide material is considered because of its strong phonon–polariton resonance properties in the sky window. The structure is designed on a double-sided polished fused silica substrate, in which air holes of depth 10  μm are etched. The air holes are arranged in a square lattice of periodicity (lattice constant) 6  μm. The structure shows its capability by reducing the temperature by 13°C from ambient under the direct sunlight.

Fig. 9

Schematic of various used approaches. (a) Color-preserving radiative cooling device with 4 α-quartz bar array on top of the original structure for strong thermal emission,113 (b) Thermal emitter with multilayer conical metamaterial pillar arrays made of Al and Ge,116 (c) Multilayer all-dielectric micropyramid structure,117 and (d) metal-loaded dielectric resonator structure.119

JNP_14_3_030901_f009.png

Hossain et al.116 designed a thermal emitter by introducing a conical metamaterial array made of Al and Ge material and arranged in a pillar-type structure as shown in Fig. 9(b). This is the first research carried out on antenna-type structures. The aluminum and germanium possess the thickness of around 30 and 110 nm, respectively. The proposed structure exhibits a radiative cooling power of 116.6  W/m2 at ambient temperature. Working further on the structure, Wu et al.117 reported a dielectric material-based micropyramid structure as shown in Fig. 9(c). The proposed design theoretically retains the best capability of radiative cooling effect of 47°C below the ambient but wide acceptability is still a concern due to its complex fabrication. Recently, Cho et al.118 reported an antenna design using tungsten (W) material. The authors designed a cone-type structure and successfully fabricated the structure using laser-interferometric lithography. They demonstrated that emission improves along with the increase of aspect ratio of cone. A simpler metal-loaded dielectric resonator structure is designed by Zou et al.119 The designed surface consists of phosphorus-doped n-type silicon and silver layer as shown in Fig. 9(d). The proposed structure is advantageous in terms of integration possibility with various silicon-based platforms.

Inspired by Morpho didius butterfly wings’ structure, Didari et al.120 presented a designer metamaterial system for radiative cooling applications. This nanophotonic structure consists of SiC material-based tree structures as shown in Fig. 10(b). The actual internal structure is schematically represented in Fig. 10(a). To enhance the spectral emissivity, the authors further optimized the structural dimensions and complete structure placed in close proximity of a thin film in a vacuum separated by nanoscale gaps as shown in Figs. 10(c) and 10(d). This modification in design improves the near-field radiative transfer within the sky window. Another studied on white beetles Goliathus has also been carried out recently.121 It possesses the unique structure comprising an exterior shell and a unique interior of packed hollow cylinders as shown in Fig. 10(e). This structure not only contributes to a lower equilibrium temperature under direct sunlight but also enhances the broadband omnidirectional reflection of solar spectrum. This is because of the thin-film interference, Mie resonance, and total internal reflection. Furthermore, the structure is also highly emissive in the MIR range. Combining all these effects, it possesses the capability to reduce their temperature approximated around 7.8°C in air. Table 3 summarizes the recent work done on designing radiative cooler based on 2D nanophotonic structure.

Fig. 10

Schematic illustration of (a) internal structure of Morpho didius butterfly wings’, (b) proposed simplified structure, (c) and (d) modified proposed structures,120 and (e) interior cylindrical structure of white beetles Goliathus.121

JNP_14_3_030901_f010.png

Table 3

Summary of the recent development in 2D nanophotonic structure.

ReferencesCooling power (W/m2)Temperature reduction (°C)YearStructure
Zhang et al.14390.85.12020Photonic film comprising a micropyramid-arrayed polymer matrix with random ceramic particles
Yang et al.14460520191-mm-thick lithium fluoride crystal coated with silver backing
Wu et al.11712247°C below the ambient temperature2018Two-dimensional pyramidal nanostructure of the radiative cooler is composed of alternating aluminum oxide (Al2O3) and silica (SiO2) multilayer thin films and a bottom silver layer
Atiganyanun et al.14542018Randomly packed low-index SiO2 microspheres
Mandal et al.1469662018Porous P(VdF-HFP) HP coating
Bao et al.14752017Two layers of TiO2, SiO2, and SiC nanoparticles
Zhai et al.148932017Micrometer-sized SiO2 spheres randomly distributed in a matrix material of TPX

5.

Future Perspective and Challenges

Development of nanophotonic devices-based passive radiator structures is a hot research topic for radiative cooling, where incorporation of photonic technology is an added advantage due to its unique capability to tailor the spectral properties of the radiator for designing an efficient daytime passive radiative cooling device. This has promoted the development of devices for subambient radiative cooling in recent years. Early research demonstrated that photonic technology-based structures can be used for these applications by thoroughly optimizing their properties to achieve better spectral emissivity for sky window while using a back-reflector for solar spectrum. Most of the reported work focuses on efficiency optimization of the device. However, this can also be designed to work selectively depending on environmental variation. For example, passive radiative cooling may not be required during winter and nighttime. Thereby, self-adapting radiators have desired those work according to different ambient temperatures.122124 Thus, it becomes desirable to adopt a material whose properties change according to environmental conditions. Phase change materials seem to be best materials for these types of designs.125,126 The phase change materials convert from one phase to other by heating them up to their transition temperature.127,128 Various phase change materials, such as VO2, Ge2Sb2Te2, and modified graphene oxide, are explored in literature.122,129,130 Working toward this direction, Ono et al.122 designed a photonic structure to realize self-adaptive radiative cooling. The authors designed a spectrally selective filter made of 11 layers of Ge/MgF2 on the top of a three-layer VO2/MgF2/W structure as shown in Fig. 11(a). Here, VO2 works as the phase change material. Similarly, Wu et al.123 also proposed a structure with VO2 [as phase change material shown in Fig. 11(d)] stacked with SiO2 and successfully demonstrated the change in cooling power by phase changing of VO2.

Fig. 11

Schematic of proposed switchable radiative cooling devices made of phase change material. (a) A spectrally selective filter made of 11 layers of Ge/MgF2 on the top of a VO2/MgF2/W structure122 and (b) VO2 stacked with SiO2 on silicon substrate.123

JNP_14_3_030901_f011.png

Furthermore, there are a number of additional challenges that need to be overcome to design an efficient radiator. The fabrication procedure of 2D and 3D photonic radiator structures is challenging that constraint them to become commercial application.131,132 Laser-interferometric lithography and femtosecond laser cross-linking techniques are explored to fabricate these complex structure.118,133 The techniques utilize a laser beam that is incident of a precursor material. The incident laser beam needs an effective control and guiding mechanism to generate such complex geometries. The femtosecond laser technique can also be used to create nanoholes array in aluminum film.134 Similarly, the 1D nanophotonic structures seem to be better as their fabrication is quite simpler than alternate 2D and 3D nanophotonic structures. Additionally, large-scale production is also difficult to achieve at present. Therefore, photonic devices-based passive radiators are still in the early development stage and restricted to laboratory research and exploration. Polymer-based radiative cooling structures are likely to be the future devices due to their significant advantage in terms of ease of manufacturability and cost.135 However, reliability and long-term stability are the main critical challenges that will always be there. Polymer degradation with time affects their long-term high solar reflectivity. The same is true for the metal, where moisture may lead to formation of metal oxide. Thereby, exploration of a new and effective material system is always required for functionality and efficiency enhancement of the radiative cooler structures.

6.

Conclusion

In this review, a thorough study in the field of daytime passive radiative cooling has been carried out, which focuses on recent progress made in the field. Reported works and their corresponding results demonstrate that photonic nanostructures play a significant role in the efficiency improvement of these devices. Furthermore, different nanophotonic structures, their radiative properties, and corresponding design mechanisms are discussed in details. Nature-inspired nanophotonic structures seem to have an edge for radiative cooling. However, their practical implementation is still in process. Furthermore, in the future, the key technologies of biomimetic daytime radiator will be the development, device integration, and explorations of new designs and methods, which will open a new way to design highly efficient passive daytime radiative coolers.

Acknowledgments

Authors acknowledge all members of ECE Department at JIIT for their help and support. Authors declare no conflicts of interest.

References

1. 

E. D. Cian et al., “Global energy consumption in a warming climate,” Environ. Resource Econ., 72 (2), 365 –410 (2019). https://doi.org/10.1007/s10640-019-00334-x Google Scholar

2. 

O. Meangbua et al., “Factors influencing energy requirements and CO2 emissions of households in Thailand: a panel data analysis,” Energy Policy, 129 521 –531 (2019). https://doi.org/10.1016/j.enpol.2019.02.050 ENPYAC 0301-4215 Google Scholar

3. 

M. I. Ahmad et al., “Introduction: overview of buildings and passive cooling technique,” Nocturnal Cooling Technology for Building Applications, Springer, Singapore (2019). Google Scholar

4. 

D. Sato et al., “Review of photovoltaic module cooling methods and performance evaluation of the radiative cooling method,” Renew. Sustain. Energy Rev., 104 151 –166 (2019). https://doi.org/10.1016/j.rser.2018.12.051 Google Scholar

5. 

M. Santamouris, Cooling Energy Solutions for Buildings and Cities, University of New South Wales, Sydney (2019). Google Scholar

6. 

D. Zhao et al., “Radiative sky cooling: fundamental principles, materials, and applications,” Appl. Phys. Rev., 6 021306 (2019). https://doi.org/10.1063/1.5087281 Google Scholar

7. 

C. D. Reid et al., “Measurement of spectral emissivity from 2  μm to 15  μm,” JOSA, 49 78 –82 (1959). https://doi.org/10.1364/JOSA.49.000078 JSDKD3 Google Scholar

8. 

H. Miyazaki et al., “Fabrication of radiative cooling devices using Si2N2O nano-particles,” J. Ceram. Soc. Jpn., 124 1185 –1187 (2016). https://doi.org/10.2109/jcersj2.16164 JCSJEW 0914-5400 Google Scholar

9. 

H. Miyazaki et al., “Fabrication of radiative cooling materials based on Si2N2O particles by the nitridation of mixtures of silicon and silicon dioxide powders,” J. Ceram. Soc. Jpn., 121 242 –245 (2013). https://doi.org/10.2109/jcersj2.121.242 JCSJEW 0914-5400 Google Scholar

10. 

B. Zho et al., “Performance analysis of a hybrid system combining photovoltaic and night time radiative cooling,” Appl. Energy, 252 113432 (2019). https://doi.org/10.1016/j.apenergy.2019.113432 Google Scholar

11. 

C. G. C. Granqvist et al., “Radiative cooling to low temperatures: general considerations and application to selectively emitting SiO films,” J. Appl. Phys., 52 4205 (1981). https://doi.org/10.1063/1.329270 JAPIAU 0021-8979 Google Scholar

12. 

R. Craig, The Upper Atmosphere: Meteorology And Physics, Academic Press, New York (1965). Google Scholar

13. 

A. Rephaeli et al., “Ultra broadband photonic structures to achieve high-performance day-time radiative cooling,” Nano Lett., 13 1457 –1461 (2013). https://doi.org/10.1021/nl4004283 NALEFD 1530-6984 Google Scholar

14. 

D. Liu et al., “A thermally stable cooler for efficient passive radiative cooling throughout the day,” Opt. Mater., 92 330 –334 (2019). https://doi.org/10.1016/j.optmat.2019.04.061 OMATET 0925-3467 Google Scholar

15. 

T. M. J. Nilsson et al., “A solar reflecting material for radiative cooling applications: ZnS pigmented polyethylene,” Sol. Energy Mater. Sol. Cells, 28 175 –193 (1992). https://doi.org/10.1016/0927-0248(92)90010-M SEMCEQ 0927-0248 Google Scholar

16. 

T. M. J. Nilsson et al., “Radiative cooling during the day: simulations and experiments on pigmented polyethylene cover foils,” Sol. Energy Mater. Sol. Cells, 37 93 –118 (1995). https://doi.org/10.1016/0927-0248(94)00200-2 SEMCEQ 0927-0248 Google Scholar

17. 

T. Mouhib et al., “Stainless steel/tin/glass coating as spectrally selective material for passive radiative cooling applications,” Opt. Mater., 31 673 –677 (2009). https://doi.org/10.1016/j.optmat.2008.07.010 OMATET 0925-3467 Google Scholar

18. 

J. Peoples et al., “A strategy of hierarchical particle sizes in nanoparticle composite for enhancing solar reflection,” Int. J. Heat Mass Transfer, 131 487 –494 (2019). https://doi.org/10.1016/j.ijheatmasstransfer.2018.11.059 IJHMAK 0017-9310 Google Scholar

19. 

H. Yuan et al., “Effective, angle-independent radiative cooler based on one-dimensional photonic crystal,” Opt. Express, 26 (21), 27885 –27893 (2018). https://doi.org/10.1364/OE.26.027885 OPEXFF 1094-4087 Google Scholar

20. 

W. Liu et al., “Multilayer thin-film meta-surface thermal emitter for radiation cooling in high-temperature devices,” in Int. Photonics and Optoelectron. Meeting, OSA Technical Digest, (2018). Google Scholar

21. 

Y. Zhu et al., “Thin films of high reflectivity for efficient radiative cooling,” Proc. SPIE, 10964 109643U (2018). https://doi.org/10.1117/12.2505995 Google Scholar

22. 

N. Athanasopoulos et al., “Programmable thermal emissivity structures based on bio-inspired self-shape materials,” Sci. Rep., 5 17682 (2015). https://doi.org/10.1038/srep17682 SRCEC3 2045-2322 Google Scholar

23. 

Z. Han et al., “Bio-inspired omnidirectional self-stable reflectors with multi-scale hierarchical structures,” ACS Appl. Mater. Interfaces, 9 29285 –29294 (2017). https://doi.org/10.1021/acsami.7b08768 AAMICK 1944-8244 Google Scholar

24. 

Z. Ouyang et al., “Photonic structures based on dielectric and magnetic one-dimensional photonic crystals for wide omnidirectional total reflection,” JOSA-B, 25 (3), 297 –301 (2008). https://doi.org/10.1364/JOSAB.25.000297 Google Scholar

25. 

D. Fu, “Radiation transfer in the atmosphere: radiation, solar,” Encyclopedia of Atmospheric Science, 1 –4 Elsevier, New York (2015). Google Scholar

26. 

J.-L. Kou et al., “Daytime radiative cooling using near-black infrared emitters,” ACS Photonics, 4 (3), 626 –630 (2017). https://doi.org/10.1021/acsphotonics.6b00991 Google Scholar

27. 

N. N. Shi et al., “Keeping cool: enhanced optical reflection and radiative heat dissipation in Saharan silver ants,” Science, 349 (6245), 298 –301 (2015). https://doi.org/10.1126/science.aab3564 SCIEAS 0036-8075 Google Scholar

28. 

R. H. Siddique et al., “Theoretical and experimental analysis of the structural pattern responsible for the iridescence of Morpho butterflies,” Opt. Express, 21 14351 –14361 (2013). https://doi.org/10.1364/OE.21.014351 OPEXFF 1094-4087 Google Scholar

29. 

S. C. Cary et al., “Worms bask in extreme temperatures,” Nature, 391 545 –546 (1998). https://doi.org/10.1038/35286 Google Scholar

30. 

W. J. Gehring et al., “Heat shock protein synthesis and thermo tolerance in Cataglyphis, an ant from the Sahara Desert,” Proc. Natl. Acad. Sci. U. S. A., 92 2994 –2998 (1995). https://doi.org/10.1073/pnas.92.7.2994 Google Scholar

31. 

D. D. Horikawa, “Survival of tardigrades in extreme environments: a model animal for astrobiology,” Cellular Origin, Life in Extreme Habitats and Astrobiology, 21 205 –217 2012). Google Scholar

32. 

S. Ling et al., “Nanofibrils in nature and materials engineering,” Nat. Rev. Mater., 3 18016 (2018). https://doi.org/10.1038/natrevmats.2018.16 Google Scholar

33. 

T. B. H. Schroeder et al., “It’s not a bug, it’s a feature: functional materials in insects,” Adv. Mater., 30 (19), 1705322 (2018). https://doi.org/10.1002/adma.201705322 ADVMEW 0935-9648 Google Scholar

34. 

X. Wu et al., “Extreme optical properties tuned through phase substitution in a structurally optimized biological photonic polycrystal,” Adv. Funct. Mater., 23 (29), 3615 –3620 (2013). https://doi.org/10.1002/adfm.201203597 AFMDC6 1616-301X Google Scholar

35. 

P. Vukusic et al., “Brilliant whiteness in ultrathin beetle scales,” Science, 315 (5810), 348 (2007). https://doi.org/10.1126/science.1134666 SCIEAS 0036-8075 Google Scholar

36. 

L. Cortese et al., “Anisotropic light transport in white beetle scales,” Adv. Opt. Mater., 3 (10), 1337 –1341 (2015). https://doi.org/10.1002/adom.201500173 2195-1071 Google Scholar

37. 

G. Smith et al., “Nanophotonics-enabled smart windows, buildings and wearables,” Nanophotonics, 5 (1), 55 –73 (2016). https://doi.org/10.1515/nanoph-2016-0014 Google Scholar

38. 

A. Krishna et al., “Morpho butterfly-inspired spectral emissivity of metallic microstructures for radiative cooling,” in 17th IEEE Intersoc. Conf. Thermal and Thermomech. Phenom. Electron. Syst., 78 –85 (2018). https://doi.org/10.1109/ITHERM.2018.8419652 Google Scholar

39. 

C. C. Tsai et al., “Butterflies regulate wing temperatures using radiative cooling,” in Conf. Lasers and Electro-Opt., (2017). Google Scholar

40. 

Q. Willot et al., “Total internal reflection accounts for the bright color of the Saharan silver ant,” PLoS One, 11 (4), e0152325 (2016). https://doi.org/10.1371/journal.pone.0152325 POLNCL 1932-6203 Google Scholar

41. 

N. N. Shi et al., “Nano-structured wild moth cocoon fibers as radiative cooling and waveguiding optical materials,” in Conf. Lasers and Electro-Opt., (2017). Google Scholar

42. 

N. N. Shi et al., “Nano-structured fibers as a versatile photonic platform: radiative cooling and waveguiding through transverse Anderson localization,” Light: Sci. Appl., 7 (37), 1 –9 (2018). https://doi.org/10.1038/s41377-018-0033-x Google Scholar

43. 

S. H. Choi et al., “Anderson light localization in biological nanostructures of native silk,” Nat. Commun., 9 452 (2018). https://doi.org/10.1038/s41467-017-02500-5 NCAOBW 2041-1723 Google Scholar

44. 

T. L. Bergman et al., Fundamentals of Heat and Mass Transfer, John Wiley & Sons, Hoboken, New Jersey (2011). Google Scholar

45. 

Y. Liu et al., “A pragmatic bilayer selective emitter for efficient radiative cooling under direct sunlight,” Materials, 12 (8), 1208 (2019). https://doi.org/10.3390/ma12081208 MATEG9 1996-1944 Google Scholar

46. 

L. Peng et al., “Design and fabrication of the ultrathin metallic film-based infrared selective radiator,” Solar Energy Mater. Solar Cells, 193 7 –12 (2019). https://doi.org/10.1016/j.solmat.2018.12.039 SOCLD4 0379-6787 Google Scholar

47. 

Y. Q. Wang et al., “Perfect electromagnetic and sound absorption via sub-wavelength holes array,” Opto-Electron. Adv., 1 (8), 180013 (2018). https://doi.org/10.29026/oea.2018.180013 Google Scholar

48. 

J. Yang et al., “Design and fabrication of broadband ultralow reflectivity black Si surfaces by laser micro/nano processing,” Light: Sci. Appl., 3 (7), e185 (2014). https://doi.org/10.1038/lsa.2014.66 Google Scholar

49. 

E. E. Bell et al., “Spectral radiance of sky and Terrain at wavelengths between 1 and 20 microns. II. Sky measurements,” J. Opt. Soc. Am., 50 (12), 1313 (1960). https://doi.org/10.1364/JOSA.50.001313 JOSAAH 0030-3941 Google Scholar

50. 

A. W. Harrison, “Effect of atmospheric humidity on radiation cooling,” Sol. Energy, 26 (3), 243 (1981). https://doi.org/10.1016/0038-092X(81)90209-7 Google Scholar

51. 

K. Y. Kondratyev, Radiation in the Atmosphere, Academic Press, New York (1969). Google Scholar

52. 

W. Wang et al., “The radiative effect of aerosols in the Earth’s atmosphere,” J. Appl. Meterol., 13 (5), 521 –534 (1974). https://doi.org/10.1175/1520-0450(1974)013<0521:TREOAI>2.0.CO;2 Google Scholar

53. 

A. V. Tikhonravov et al., “Application of the needle optimization technique to the design of optical coatings,” Appl. Opt., 35 5493 –5508 (1996). https://doi.org/10.1364/AO.35.005493 APOPAI 0003-6935 Google Scholar

54. 

A. V. Tikhonravov et al., “Optical coating design approaches based on the needle optimization technique,” Appl. Opt., 46 704 –710 (2007). https://doi.org/10.1364/AO.46.000704 APOPAI 0003-6935 Google Scholar

55. 

T. Boudet et al., “Thin-film designs by simulated annealing,” Appl. Opt., 35 6219 –6226 (1996). https://doi.org/10.1364/AO.35.006219 APOPAI 0003-6935 Google Scholar

56. 

L. Li et al., “Jump method for optical thin film design,” Opt. Express, 17 16920 –16926 (2009). https://doi.org/10.1364/OE.17.016920 OPEXFF 1094-4087 Google Scholar

57. 

Y. Shi et al., “Optimization of multilayer optical films with a memetic algorithm and mixed integer programming,” ACS Photonics, 5 684 –691 (2018). https://doi.org/10.1021/acsphotonics.7b01136 Google Scholar

58. 

C. G. Granqvist et al., “Radiative cooling to low temperatures with selectivity IR-emitting surfaces,” Thin Solid Films, 90 187 –190 (1982). https://doi.org/10.1016/0040-6090(82)90648-4 THSFAP 0040-6090 Google Scholar

59. 

S. Catalanotti et al., “The radiative cooling of selective surfaces,” Sol. Energy, 17 83 –89 (1975). https://doi.org/10.1016/0038-092X(75)90062-6 Google Scholar

60. 

B. Orel et al., “Radiative cooling efficiency of white pigmented paints,” Sol. Energy, 50 477 –482 (1993). https://doi.org/10.1016/0038-092X(93)90108-Z Google Scholar

61. 

T. S. Eriksson et al., “Surface coatings for radiative cooling applications: silicon dioxide and silicon nitride made by reactive RF sputtering,” Sol. Energy Mater., 12 319 –325 (1985). https://doi.org/10.1016/0165-1633(85)90001-2 SOEMDH 0165-1633 Google Scholar

62. 

H. S. Dutta, A. K. Goyal and S. Pal, “Analysis of dispersion diagram for high performance refractive index sensor based on photonic crystal waveguides,” Photonics Nanostruct. – Fundam. Appl., 23 21 –27 (2017). https://doi.org/10.1016/j.photonics.2016.11.004 Google Scholar

63. 

J. D. Joannopoulos et al., Photonic Crystals: Molding the Flow of Light, Princeton University Press, New Jersey (2008). Google Scholar

64. 

T. Baba, “Slow light in photonic crystals,” Nat. Photonics, 2 465 –473 (2008). https://doi.org/10.1038/nphoton.2008.146 NPAHBY 1749-4885 Google Scholar

65. 

A. K. Goyal et al., “Porous photonic crystal structure for sensing applications,” J. Nanophotonics, 12 (4), 040501 (2018). https://doi.org/10.1117/1.JNP.12.040501 1934-2608 Google Scholar

66. 

A. K. Goyal et al., “Performance optimization of photonic crystal resonator based sensor,” Opt. Quantum Electron., 48 431 (2016). https://doi.org/10.1007/s11082-016-0701-0 OQELDI 0306-8919 Google Scholar

67. 

H. S. Dutta et al., “Sensitivity enhancement in photonic crystal waveguide platform for refractive index sensing applications,” J. Nanophotonics, 8 (1), 083088 (2014). https://doi.org/10.1117/1.JNP.8.083088 1934-2608 Google Scholar

68. 

Z. Li et al., “Two designs of thin film for cooling buildings based on photonic crystal,” in Int. Conf. Ind. Electron. and Appl., (2015). Google Scholar

69. 

A. Ghanekar et al., “Photonic metamaterials: controlling nanoscale radiative thermal transport,” Heat Transfer-Models, Methods and Applications, IntechOpen, London (2017). Google Scholar

70. 

H. Zhou et al., “Bio-inspired photonic materials: prototypes and structural effect designs for applications in solar energy manipulation,” Adv. Funct. Mater., 28 1705309 (2018). https://doi.org/10.1002/adfm.201705309 AFMDC6 1616-301X Google Scholar

71. 

K. Xu et al., “Micro optical sensors based on avalanching silicon light-emitting devices monolithically integrated on chips,” Opt. Mater. Express, 9 3985 –3997 (2019). https://doi.org/10.1364/OME.9.003985 Google Scholar

72. 

A. K. Goyal et al., “Porous multilayer photonic band gap structure for optical sensing,” in OSA Tech. Digest, (2016). https://doi.org/10.1364/PHOTONICS.2016.Tu4A.12 Google Scholar

73. 

A. K. Goyal and S. Pal, “Design analysis of Bloch surface wave based sensor for haemoglobin concentration measurement,” Appl. Nanosci., (2020). https://doi.org/10.1007/s13204-020-01437-4 Google Scholar

74. 

M. Hossain et al., “Radiative cooling: principles, progress, and potentials,” Adv. Sci., 3 1500360 (2016). https://doi.org/10.1002/advs.201500360 Google Scholar

75. 

Y. Zahu et al., “A multilayer emitter close to ideal solar reflectance for efficient daytime radiative cooling,” Polymers, 11 (7), 1203 (2019). https://doi.org/10.3390/polym11071203 Google Scholar

76. 

Z. Huang et al., “Nano-particle embedded double-layer coating for daytime radiative cooling,” Int. J. Heat Mass Transf., 104 890 –896 (2017). https://doi.org/10.1016/j.ijheatmasstransfer.2016.08.009 Google Scholar

77. 

L. Zhu et al., “Radiative cooling of solar cells,” Optica, 1 32 –38 (2014). https://doi.org/10.1364/OPTICA.1.000032 Google Scholar

78. 

E. Yablonovitch, “Inhibited spontaneous emission in solid-state physics and electronics,” Phys. Rev., 58 (20), 2059 –2062 (1987). https://doi.org/10.1103/PhysRevLett.58.2059 PHRVAO 0031-899X Google Scholar

79. 

A. K. Goyal et al., “Recent advances and progress in photonic crystal-based gas sensors,” J. Phys. D: Appl. Phys., 50 (20), 203001 (2017). https://doi.org/10.1088/1361-6463/aa68d3 JPAPBE 0022-3727 Google Scholar

80. 

Y. Fink et al., “An omni-directional reflector,” Science, 282 1679 (1998). https://doi.org/10.1126/science.282.5394.1679 SCIEAS 0036-8075 Google Scholar

81. 

J. N. Winn et al., “Omnidirectional reflection from a one-dimensional photonic crystal,” Opt. Lett., 23 1573 (1998). https://doi.org/10.1364/OL.23.001573 OPLEDP 0146-9592 Google Scholar

82. 

B. Gallas et al., “Making an omni-directional reflector,” Appl. Opt., 40 5056 (2001). https://doi.org/10.1364/AO.40.005056 APOPAI 0003-6935 Google Scholar

83. 

X. Wang et al., “Enlargement of omnidirectional total reflection frequency range in one-dimensional photonic crystals by using photonic heterostructures,” Appl. Phys. Lett., 80 4291 (2002). https://doi.org/10.1063/1.1484547 APPLAB 0003-6951 Google Scholar

84. 

C. Zhang et al., “Enlargement of omnidirectional total reflection frequency range in one-dimensional photonic crystals by using photonic hetero-structures,” Appl. Phys. Lett., 87 3174 (2000). https://doi.org/10.1063/1.372318 APPLAB 0003-6951 Google Scholar

85. 

S. Joseph et al., “Omnidirectional reflector using one-dimensional dispersive photonic hetero-structure,” Optik, 125 2734 –2738 (2014). https://doi.org/10.1016/j.ijleo.2013.11.071 OTIKAJ 0030-4026 Google Scholar

86. 

M. Upadhyay et al., “Infrared omnidirectional mirror based on one-dimensional birefringent-dielectric photonic crystal,” PIER M, 25 211 (2012). https://doi.org/10.2528/PIERM12061802 Google Scholar

87. 

R. Kumar et al., “Study of one-dimensional nano-layered graded photonic crystal consisting of birefringent and dielectric materials,” Photonics Nanostruct. – Fundam. Appl., 28 20 –31 (2018). https://doi.org/10.1016/j.photonics.2017.11.002 Google Scholar

88. 

T. M. Jordan et al., “Non-polarizing broadband multilayer reflectors in fish,” Nat Photonics, 6 (11), 759 –763 (2012). https://doi.org/10.1038/nphoton.2012.260 Google Scholar

89. 

S. Zhao et al., “Broadband and polarization reflectors in the lookdown, Selene vomer,” J. R. Soc. Interface, 12 20141390 (2015). https://doi.org/10.1098/rsif.2014.1390 1742-5689 Google Scholar

90. 

E. J. Denton et al., “Polarization of light reflected from the silvery exterior of the bleak, Alburnus alburnus,” J. Mar. Biol. Assoc. U.K., 45 (3), 705 –709 (1965). https://doi.org/10.1017/S0025315400016532 JMBAAK 0025-3154 Google Scholar

91. 

A. Adibi et al., “Secondary grating formation by readout at Bragg-null incidence,” Appl. Opt., 38 4291 –4295 (1999). https://doi.org/10.1364/AO.38.004291 APOPAI 0003-6935 Google Scholar

92. 

E. Rephaeli et al., “Ultra broad band photonic structures to achieve high-performance daytime radiative cooling,” Nano Lett., 13 (4), 1457 –1461 (2013). https://doi.org/10.1021/nl4004283 NALEFD 1530-6984 Google Scholar

93. 

P. Raman et al., “Passive radiative cooling below ambient air temperature under direct sunlight,” Nature, 515 540 (2014). https://doi.org/10.1038/nature13883 Google Scholar

94. 

M. A. Kecebas et al., “Passive radiative cooling design with broadband optical thin-film filters,” J. Quant. Spectrosc. Rad. Transfer, 198 179 –86 (2017). https://doi.org/10.1016/j.jqsrt.2017.03.046 Google Scholar

95. 

S. Y. Jeong et al., “Field investigation of a photonic multi-layered TiO2 passive radiative cooler in sub-tropical climate,” Renew. Energy, 146 44 –55 (2020). https://doi.org/10.1016/j.renene.2019.06.119 RNENE3 0960-1481 Google Scholar

96. 

Y. Fu et al., “Daytime passive radiative cooler using porous alumina,” Solar Energy Mater. Solar Cells, 191 50 –54 (2019). https://doi.org/10.1016/j.solmat.2018.10.027 SOCLD4 0379-6787 Google Scholar

97. 

Z. Chen et al., “Radiative cooling to deep sub-freezing temperatures through a 24-h day–night cycle,” Nat. Commun., 7 13729 (2016). https://doi.org/10.1038/ncomms13729 NCAOBW 2041-1723 Google Scholar

98. 

Y. Huang et al., “Broadband metamaterial as an ‘invisible’ radiative cooling coat,” Opt. Commun., 407 204 –207 (2018). https://doi.org/10.1016/j.optcom.2017.09.036 OPCOB8 0030-4018 Google Scholar

99. 

B. Bartoli et al., “Nocturnal and diurnal performances of selective radiators,” Appl. Energy, 3 (4), 267 –286 (1977). https://doi.org/10.1016/0306-2619(77)90015-0 Google Scholar

100. 

B. Landro et al., “Effect of surface characteristics and atmospheric conditions on radiative heat loss to a clear sky,” Int. J. Heat Mass Transfer, 23 (5), 613 –620 (1980). https://doi.org/10.1016/0017-9310(80)90004-6 IJHMAK 0017-9310 Google Scholar

101. 

B. Zho et al., “General strategy of passive sub-ambient daytime radiative cooling,” Solar Energy Mater. Solar Cells, 199 108 –113 (2019). https://doi.org/10.1016/j.solmat.2019.04.028 SOCLD4 0379-6787 Google Scholar

102. 

M. Hu et al., “Field test and preliminary analysis of a combined diurnal solar heating and nocturnal radiative cooling system,” Appl. Energy, 179 899 –908 (2016). https://doi.org/10.1016/j.apenergy.2016.07.066 ENGYD4 0149-9386 Google Scholar

103. 

A. R. Gentle et al., “A sub-ambient open roof surface under the mid-summer sun,” Adv. Sci., 2 1500119 (2015). https://doi.org/10.1002/advs.201500119 Google Scholar

104. 

P. Yang et al., “A dual-layer structure with record-high solar reflectance for day time radiative cooling,” Sol. Energy, 169 316 –324 (2018). https://doi.org/10.1016/j.solener.2018.04.031 Google Scholar

105. 

E. D. Palik, Handbook of Optical Constants of Solids, Academic Press, Orlando, Florida (1985). Google Scholar

106. 

K. Yao et al., “Near-perfect selective photonic crystal emitter with nanoscale layers for daytime radiative cooling,” ACS Appl. Nano Mater., 2 (9), 5512 –5519 (2019). https://doi.org/10.1021/acsanm.9b01097 Google Scholar

107. 

C. Sheng et al., “Colored radiative cooler under optical Tamm resonance,” ACS Photonics, 6 (10), 2545 –2552 (2019). Google Scholar

108. 

K. Xu, “Silicon MOS optoelectronic micro-nano structure based on reverse-biased PN junction,” Phys. Status Solidi A, 216 1800868 (2019). https://doi.org/10.1002/pssa.201800868 PSSABA 1862-6300 Google Scholar

109. 

W. Li et al., “Nano-photonic control of thermal radiation for energy applications [invited],” Opt. Express, 26 15995 (2018). https://doi.org/10.1364/OE.26.015995 OPEXFF 1094-4087 Google Scholar

110. 

Y. Zheng et al., “Sensing and lasing applications of whispering gallery mode micro-resonators,” Opto-Electron. Adv., 1 (9), 180015 (2018). https://doi.org/10.29026/oea.2018.180015 Google Scholar

111. 

A. E. Kaplan et al., “Tunable narrow band optical reflector based on indirectly coupled micro ring resonators,” Opt. Express, 28 13497 –13515 (2020). https://doi.org/10.1364/OE.389830 OPEXFF 1094-4087 Google Scholar

112. 

A. K. Goyal et al., “Design and analysis of photonic crystal micro-cavity based optical sensor platform,” AIP Conf. Proc., 1724 020005 (2016). https://doi.org/10.1063/1.4945125 APCPCS 0094-243X Google Scholar

113. 

L. Zhu et al., “Color-preserving daytime radiative cooling,” Appl. Phys. Lett., 103 223902 (2013). https://doi.org/10.1063/1.4835995 APPLAB 0003-6951 Google Scholar

114. 

W. Li et al., “Photonic thermal management of coloured objects,” Nat. Commun., 9 4240 (2018). https://doi.org/10.1038/s41467-018-06535-0 NCAOBW 2041-1723 Google Scholar

115. 

L. Zhu et al., “Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody,” Proc. Natl. Acad. Sci. U. S.A., 112 12282 –12287 (2015). https://doi.org/10.1073/pnas.1509453112 Google Scholar

116. 

M. M. Hossain et al., “A metamaterial emitter for highly efficient radiative cooling,” Adv. Opt. Mater., 3 1047 –1051 (2015). https://doi.org/10.1002/adom.201500119 2195-1071 Google Scholar

117. 

D. Wu et al., “The design of ultra-broadband selective near-perfect absorber based on photonic structures to achieve near-ideal daytime radiative cooling,” Mater. Des., 139 104 –111 (2018). https://doi.org/10.1016/j.matdes.2017.10.077 MADSD2 0264-1275 Google Scholar

118. 

J. Cho et al., “Visible to near-infrared thermal radiation from nano-structured tungsten antennas,” J. Opt., 20 09LT01 (2018). https://doi.org/10.1088/2040-8986/aad708 Google Scholar

119. 

C. Zou et al., “Metal-loaded dielectric resonator metasurfaces for radiative cooling,” Adv. Opt. Mater., 5 1700460 (2017). https://doi.org/10.1002/adom.201700460 2195-1071 Google Scholar

120. 

A. Didari et al., “A biomimicry design for nanoscale radiative cooling applications inspired by Morpho didius butterfly,” Sci. Rep., 8 16891 (2018). https://doi.org/10.1038/s41598-018-35082-3 SRCEC3 2045-2322 Google Scholar

121. 

D. Xie et al., “Broadband omnidirectional light reflection and radiative heat dissipation in white beetles Goliathus goliatus,” Soft Matter., 15 4294 –4300 (2019). https://doi.org/10.1039/C9SM00566H SMOABF 1744-683X Google Scholar

122. 

M. Ono et al., “Self-adaptive radiative cooling based on phase change materials,” Opt. Express, 26 A777 –A787 (2018). https://doi.org/10.1364/OE.26.00A777 OPEXFF 1094-4087 Google Scholar

123. 

S. R. Wu et al., “Passive temperature control based on a phase change metasurface,” Sci. Rep., 8 7684 (2018). https://doi.org/10.1038/s41598-018-26150-9 SRCEC3 2045-2322 Google Scholar

124. 

Y. Qu et al., “Tunable dual-band thermal emitter consisting of single-sized phase-changing GST nanodisks,” Opt. Express, 26 4279 –4287 (2018). https://doi.org/10.1364/OE.26.004279 OPEXFF 1094-4087 Google Scholar

125. 

A. Gentle et al., “Design, control, and characterization of switchable radiative cooling,” Proc. SPIE, 10759 107590L (2018). https://doi.org/10.1117/12.2323877 Google Scholar

126. 

K. Sun et al., “Metasurface optical solar reflectors using AZO transparent conducting oxides for radiative cooling of spacecraft,” ACS Photonics, 5 495 –501 (2018). https://doi.org/10.1021/acsphotonics.7b00991 Google Scholar

127. 

A. J. Noel et al., “Phase change materials,” Storing Energy, 249 –272 Elsevier, New York (2016). Google Scholar

128. 

X. Zhilin et al., “Easy way to achieve self-adaptive cooling of passive radiative materials,” ACS Appl. Mater. Interfaces, 12 (24), 27241 –27248 (2020). https://doi.org/10.1021/acsami.0c05803 AAMICK 1944-8244 Google Scholar

129. 

Y. G. Chen et al., “Hybrid phase-change plasmonic crystals for active tuning of lattice resonances,” Opt. Express, 21 (11), 13691 –13698 (2013). https://doi.org/10.1364/OE.21.013691 OPEXFF 1094-4087 Google Scholar

130. 

G. Y. Cao et al., “An accurate design of graphene oxide ultrathin flat lens based on Rayleigh–Sommerfeld theory,” Opto-Electron. Adv., 1 180012 (2018). https://doi.org/10.29026/oea.2018.180012 Google Scholar

131. 

A. K. Goyal et al., “Realization of large-scale photonic crystal cavity-based devices,” J. Micro/Nanolithogr. MEMS MOEMS, 15 (3), 031608 (2016). https://doi.org/10.1117/1.JMM.15.3.031608 Google Scholar

132. 

H. S. Dutta et al., “Fabrication of photonic crystal line defect waveguides by use of optical lithography and focused ion beam,” in OSA Tech. Digest, (2016). https://doi.org/132: 10.1364/PHOTONICS.2016.W4E.4 Google Scholar

133. 

D. Serien and K. Sugioka, “Fabrication of three-dimensional proteinaceous micro- and nano-structures by femtosecond laser cross-linking,” Opto-Electron. Adv., 1 (4), 180008 (2018). https://doi.org/10.29026/oea.2018.180008 Google Scholar

134. 

H. Liu et al., “Self-organized periodic microholes array formation on aluminium surface via femtosecond laser ablation induced incubation effect,” Adv. Funct. Mater., 29 (42), 1903576 (2019). https://doi.org/10.1002/adfm.201903576 AFMDC6 1616-301X Google Scholar

135. 

M. Santamouris and J. Feng, “Recent progress in daytime radiative cooling: is it the air conditioner of the future?,” Buildings, 8 168 (2018). https://doi.org/10.3390/buildings8120168 Google Scholar

136. 

“Reference solar spectral irradiance: air mass 1.5,” http://rredc.nrel.gov/solar/spectra/am1.5/ Google Scholar

137. 

O. del Barco et al., “Omnidirectional high-reflectivity mirror in the 420  μm spectral range,” J. Opt., 19 065102 (2017). https://doi.org/10.1088/2040-8986/aa6c76 Google Scholar

138. 

K. Ratra et al., “Design and analysis of broadband reflector for passive radiative cooling,” in Int. Conf. Signal Process. and Commun., 300 –303 (2019). https://doi.org/10.1109/ICSC45622.2019.8938212 Google Scholar

139. 

K. Ratra et al., “Design and analysis of omni-directional solar spectrum reflector using one-dimensional photonic crystal,” J. Nanophotonics, 14 (2), 026005 (2020). https://doi.org/10.1117/1.JNP.14.026005 1934-2608 Google Scholar

140. 

B. A. Castillo et al., “A wide band porous silicon omnidirectional mirror for the near infrared range,” J. Appl. Phys., 127 203106 (2020). https://doi.org/10.1063/1.5144621 JAPIAU 0021-8979 Google Scholar

141. 

B. Zhao et al., “Performance evaluation of daytime radiative cooling under different clear sky conditions,” Appl. Thermal Eng., 155 660 –666 (2019). https://doi.org/10.1016/j.applthermaleng.2019.04.028 ATENFT 1359-4311 Google Scholar

142. 

X. Ao et al., “Preliminary experimental study of a specular and a diffuse surface for daytime radiative cooling,” Solar Energy Mater. Solar Cells, 191 290 –296 (2019). https://doi.org/10.1016/j.solmat.2018.11.032 SEMCEQ 0927-0248 Google Scholar

143. 

H. Zhang et al., “Biologically inspired flexible photonic films for efficient passive radiative cooling,” Proc. Natl. Acad. Sci. U. S. A., 117 (26), 14657 –14666 (2020). https://doi.org/10.1073/pnas.2001802117 Google Scholar

144. 

Y. Yang et al., “Bulk material based selective infrared emitter for sub-ambient daytime radiative cooling,” Sol. Energy Mater. Sol. Cells, 211 110548 (2019). https://doi.org/10.1016/j.solmat.2020.110548 Google Scholar

145. 

S. Atiganyanun et al., “Effective radiative cooling by paint-format micro-sphere based photonic random media,” ACS Photonics, 5 1181 –1187 (2018). https://doi.org/10.1021/acsphotonics.7b01492 Google Scholar

146. 

J. Mandal et al., “Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling,” Science, 362 315 –319 (2018). https://doi.org/10.1126/science.aat9513 SCIEAS 0036-8075 Google Scholar

147. 

H. Bao et al., “Double-layer nano-particle based coatings for efficient terrestrial radiative cooling,” Sol. Energy Mater. Sol. Cell., 168 78 –84 (2017). https://doi.org/10.1016/j.solmat.2017.04.020 SEMCEQ 0927-0248 Google Scholar

148. 

Y. Zhai et al., “Scalable manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling,” Science, 355 1062 –1066 (2017). https://doi.org/10.1126/science.aai7899 SCIEAS 0036-8075 Google Scholar

Biographies of the authors are not available.

© 2020 Society of Photo-Optical Instrumentation Engineers (SPIE)
Amit Kumar Goyal and Ajay Kumar "Recent advances and progresses in photonic devices for passive radiative cooling application: a review," Journal of Nanophotonics 14(3), 030901 (13 August 2020). https://doi.org/10.1117/1.JNP.14.030901
Received: 28 May 2020; Accepted: 29 July 2020; Published: 13 August 2020
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