Fig. 1. (a) Free space radiation of black body; (b) the thermal radiation between two neighboring black bodies.(a) 黑体向自由空间的热辐射; (b)两个黑体间的热辐射

Fig. 2. (a) Thermal transfer between nanoparticle and surrounding media; (b) radiation spectrum of black body (black dashed line) and of true nanoparticles (red solid line); (c) thermal radiation of nanoparticle on the certain substrate; (d) thermal radiation enabled energy transfer between two nanoparticles.(a) 纳米颗粒与环境的热交换; (b)黑体辐射曲线(黑色虚线)和真实颗粒的辐射曲线(红色实线); (c)颗粒在一个衬底表面的热辐射; (d)两个颗粒间的热辐射能量交换

Fig. 3. Distance dependent thermal conductivity of parallel plates, in the condition of (a) room temperature^[17] and (b) low temperature^[18]. 平行板实验中在(a)室温^[17]和(b)低温^[18]条件下测得的热导率随间距的变化关系

Fig. 4. (a) Setup schematic of near-field thermal scanning microscopy^[22]; (b) schematic of spherical tips for near-field thermal scanning^[24]; (c) tips enabled nonlocal effect in thermal radiation^[26]; (d) thermal radiation speed of micro integration device^[27]. (a)热轮廓扫描仪示意图^[22]; (b)测量近场热辐射的球型针尖示意图^[24]; (c)针尖热辐射测量中的非局域效应^[26]; (d)集成化微器件中的热辐射速率测量^[27]

Fig. 5. (a) Near-field thermal radiation between parallel graphene^[28]; (b) near-field enhanced thermal radiation in boron nitride-graphene-boron nitride structure^[29]; (c) superfast thermal radiation between parallel graphene disc^[33]. (a)两层平行石墨烯间的近场热辐射传导^[28]; (b)氮化硼-石墨烯-氮化硼结构中的近场增强热辐射^[29]; (c)两个石墨烯圆盘中的超快热辐射^[33]

Fig. 6. Schematic (a) and theoretical simulation result (b) of enhanced far-field thermal radiation between parallel nanoplate^[36]. Architecture (c) and experimental result (d) of thermal radiation between parallel plate^[37]. 两个并列纳米平板间的远场热辐射增强示意图(a)和计算结果(b)^[36]; 平行板热辐射结构(c)和实验结果(d)^[37]

Fig. 7. (a) Energy transfer schematic of radiative cooling; (b) radiation windows of atmosphere and the corresponding black body radiation^[7]. (a)辐射制冷中的热量转移过程示意图; (b)大气的辐射波段和对应黑体辐射强度的对比^[7]

Fig. 8. (a) Multi-layered hole array structure (top), of which the radiative cooling could work in the daytime, and the corresponding absorption and radiation spectra (bottom)^[46]; (b) detail of layered structure^[47]; (c) temperature comparison between the radiative cooling film and the other films^[47]. (a)可实现日间辐射制冷的周期孔洞多层膜微纳结构(上图)及其吸收和辐射谱(下图)^[46]; (b)多层膜结构细节^[47]; (c)辐射制冷薄膜和其他薄膜对照物的温度变化曲线^[47]

Fig. 9. Low-cost radiative cooling materials: (a) SiO₂ beads embedded polymer film^[50], in panel (a), (i) structure schematic, and (ii) temperature changing in 3-days-nonstopping measurements; (b) coated porous polymer film^[51], in panel (b), (i) scanning electron microscope imaging and molecular structure schematic, (ii) camera picture of variously coated film, (iii) energy changing during noon time, and the corresponding radiative cooling efficiency. 低成本纳米结构辐射制冷材料　(a)二氧化硅小球掺杂的高聚物薄膜^[50], (i)结构示意图, (ii)连续三天的温度变化; (b) 涂布聚合物多孔薄膜^[51], (i)结构电子显微镜图及分子结构示意图, (ii)不同辐射制冷材料覆盖膜的照片, (iii)在中午时的能量变化以及辐射制冷降温效果曲线

Fig. 10. (a) General radiative cooling system, delivered by Fan’s group^[54], and the corresponding cooling result, of which the average cooling power is over 40 W/m²; (b) buildings used radiative cooling system, delivered by Yang’s group^[56](a) Fan团队制作的辐射制冷系统工作原理图及制冷效果^[54], 平均制冷功率超过40 W/m²; (b) Yang 团队搭建的建筑辐射制冷系统^[56]

Fig. 11. (a) Principle of radiative cooling cloth^[59]; (b) camera picture and scanning electron microscope imaging of radiative cooling textiles^[58]; (c) cooling effect on human skin^[59]; (d) radiation spectrum of radiative cooling textiles, ranging from visible to infrared frequency^[58]. (a)辐射降温衣物的工作原理^[59]; (b)辐射降温织物的照片及扫描电子显微镜图^[58]; (c)皮肤温度降温效果^[59]; (d)降温织物在可见及红外波段的辐射谱^[58]

Fig. 12. (a) Principle of radiative cooling effect enabled condensate water^[70]; (b) multi-layered radiative cooling system for condensate water^[70]; emissivity spectrum (c) of multi-layered radiative cooling system, and (d) the dramatically increased condensate water^[70]. (a)辐射制冷薄膜增加冷凝水量的工作原理^[70]; (b)多层膜冷凝水收集设备^[70]; (c)辐射制冷薄膜的发射谱以及(d)冷凝水增量效果^[70]

Fig. 13. (a) Commercial solar cell unit (I) and the lab developed unit with silver wire electrode and alumina back electrode (II); the right figure shows the corresponding camera picture with coated cooling film and the detailed cross-section of the film^[73]; (b) absorption spectra comparison between commercial solar cells unit (Fig. 13(a) I) with or without radiative cooling film, and lab made solar cell unit (Fig. 13(a) II)^[73]; (c) radiation spectra of corresponding solar cell unit, in the frequency region of atmospherically radiative window^[73]. (a) I为商业太阳能电池照片, II为实验制作的银线电极及铝背电极的太阳能电池, 右图为太阳能电池覆盖上制冷薄膜的照片及其截面示意图^[73]; (b)各个器件的吸收谱, 分别为I图中太阳能电池板有无制冷薄膜下的吸收光谱和II图中器件的吸收光谱^[73]; (c)对应器件在大气窗口的辐射谱^[73]