The Design And Fabrication Of Selective Absorber With Well-Controlled Micro-Structure

The energy-deficient problem is getting worse and the environment is deteriorating since the 21st century due to the constantly consumption of fossil fuel.The development of clean energy source and the restraining of global warming has become the major challenges in worldwide as a result.In recent years,with the rapid development of micro-nano photonics,micro-nano optical materials with tunable spectrum has exhibited great potential in the field of new energy.For the materials with high emissivity in mid-IR range as well as high reflectance in visible range,it is capable of realizing outstanding radiative-cooling performance,which can efficiently relieve the stress of excessive consumption of fossil fuels.Furthermore,high-efficiency solar-to-heat conversion process can be easily obtained through materials with high solar absorption within the full spectrum of solar light,which not only provides new method of utilizing solar energy,but also offers the possibility of mitigating the water-shortage situation in remote areas.However,the difficulty of effectively tune the optical properties of different materials to match their designs remains the major problem that restricts the development of radiative-cooling and solar-heating materials.In this article,new materials with tuned optical properties in full spectrum are proposed which can conveniently realize radiative cooling and high-efficiency solar-vapor generation separately.In the first part,properties of materials with plasmon enhanced solar absorption is presented as well as its fabrication process and solar-vapor-generating performance.The cheap NiNPs/AAO solar absorber can be made through ion sputtering deposition process,and possess ultrabroadband absorption due to the plasmonic.The absorption can be raised over 97%and the evaporation rate can reach about 0.9 kg m^-2h^-1 under one sun illumination,which is identical with theoretical calculation results.Moreover,new AuNPs/AAO absorber was also fabricated through ion beam etching process.By analyzing the energy conversion during the evaporating process,it is found that about 98W/m² more input energy can be provided and the radiation and conduction heat loss was successfully reduced.The overall efficiency was increased by 10%.In the second part,a fabrication process of polymethyl methacrylate（PMMA）membrane is developed and demonstrated,as well as the characterization of the radiative cooling performance.The membrane is fabricated through electrostatic spinning technique,it’s absorptivity/emissivity within the full spectrum is similar as radiative cooling materials.In UV and NIR range,the PMMA membrane showed a high reflectivity as well as 98.27%emissivity within atmospheric window.A radiative cooling device based on the as fabricated PMMA membrane was also installed and tested.In midday（～1100 W/m² light intensity）,it was capable of lowering the temperature by 4℃.