Sub-ambient full-color passive radiative cooling under sunlight based on effcient quantum-dot photoluminescence

基于高效光致发光的彩色亚环境辐射制冷器

Daytime radiative cooling with high solar refection and mid-infrared emission offers a sustainable way for cooling without energy consumption.However,so far sub-ambient daytime radiative coolers typically possess white/silver color with limited aesthetics and applications.Although various colored radiative cooling designs have been pursued previously,multi-colored daytime radiative cooling to a temperature below ambient has not been realized as the solar thermal effect in the visible range lead to signifcant thermal load.Here,we demonstrate that photoluminescence(PL)based colored radiative coolers(PCRCs)with high internal quantum effciency enable sub-ambient full-color cooling.As an example of experimental demonstration,we develop a scalable electrostatic-spinning/inkjet printing approach to realize the sub-ambient multi-colored radiative coolers based on quantum-dot photoluminescence.The unique features of obtained PCRCs are that the quantum dots atop convert the ultraviolet–visible sunlight into emitted light to minimize the solar-heat generation,and cellulose acetate based nanofbers as the underlayer that strongly refect sunlight and radiate thermal load.As a result,the green,yellow and red colors of PCRCs achieve temperatures of 5.4–2.2℃ below ambient under sunlight(peak solar irradiance>740 Wm),respectively.With the excellent cooling performance and scalable process,our designed PCRC opens a promising pathway towards colorful applications and scenarios of radiative cooling.

日间辐射冷却技术借助材料对太阳光高反射和对中红外大气窗口高发射的光谱特点,提供了一种零耗能的可持续制冷方案.然而,目前辐射冷却器因为实现对太阳光的高反射通常呈现出白色/银色,限制了其实际应用.开发彩色辐射冷却器则至关重要,但由于显示颜色往往导致对太阳光可见光波段的吸收,增加了体系的热负荷,所以实现彩色辐射制冷亚环境冷却一直是个挑战.本文提出了基于高量子发光效率的光致发光彩色辐射冷却器(PCRC),它可以实现全色谱亚环境日间辐射冷却.此外,作者还报道了一种可大规模生产的静电纺丝/喷墨打印方法制备PCRC.PCRC上层的光致发光着色剂实现显色的同时,将因为显色吸收的太阳光在可见光波段转化为发射光,极大地减少了太阳光对体系的加热效应;底层的醋酸纤维素纳米纤维膜能反射其余波段的太阳光并向宇宙辐射热量.这种基于光致发光的彩色辐射制冷器在太阳光直射(辐射峰值>740 W m^(-2))下,其温度比环境温度低2.2~5.4℃,实现了亚环境日间辐射冷却.该设计策略和可放大的图案化制备技术为辐射冷却的多场景应用开辟了一条新道路,并为可持续能源发展提供了一种创新途径.