Broadband Highly Absorbing Solar Absorbers Based On Two-dimensional Photonic Crystals

Since human society began to explore and use fossil fuels,the social productive forces have been developing and progressing.With the development of social productive forces,economic and technological progress,the demand for energy is increasing.The use of a large number of fossil fuels has led to the emission of greenhouse gases such as carbon dioxide and the generation of harmful substances,resulting in the rise of global temperature and environmental pollution.Since the 21 st century,human society has paid more and more attention to the development and utilization of clean energy.As the most abundant,widely distributed and directly used solar energy in clean energy,it has been the focus of scientific researchers in recent years.Spectral selective solar absorber is the core device of solar energy utilization,which is widely used in solar photothermal conversion system,solar thermal photovoltaic system.However,at present,the performance of some solar absorbers is not high because of the low overall absorption rate,narrow absorption bandwidth,poor spectral selectivity,polarization sensitivity,poor wide-angle absorption capacity and so on.In order to improve the performance of the absorber,two kinds of spectral selective solar absorbers with antireflective layer based on two-dimensional photonic crystal cavity filled with dielectric are proposed,which achieve the characteristics of all solar spectral high absorption,spectral selectivity,polarization insensitive and wide-angle absorption.COMSOL Multiphysics simulation software is used to simulate the absorption characteristics and electric field distribution of the absorber.The influence of device structure parameters on the absorption characteristics and the absorption mechanism of the device are analyzed.The main contents and innovations are as follows:1.A spectrum selective solar absorber with circular cavity of two-dimensional photonic crystal structure in tungsten substrate filled with gallium arsenide and an antireflective layer was designed.The absorption bandwidth is 300-2500 nm,including99.13% of the solar radiation energy,and the solar absorption efficiency is 94.9%.The absorption properties are determined by antireflective layer,cavity resonance and surface plasmon effect.Compared with previous studies,the absorber has a wider wavelength range,which can be defined as all solar spectrum,and has the characteristics of spectral selectivity,broadband high absorption,polarization insensitive and wide-angle absorption.2.In order to adapt to the high-temperature photovoltaic system and match the properties of photovoltaic cells,considering the thermal radiation loss,a spectrum selective solar absorber with a rectangular cavity of two-dimensional photonic crystal structure in tungsten substrate filled with hafnium dioxide and antireflective.The solar absorption efficiency of the absorber is 96.32%,and the average absorption is 97.29% in the range of300-2000 nm.When the temperature is 1300 k and the concentration coefficient is 200,the solar thermal conversion efficiency is 81.96%,and the radiation efficiency is 0.2307.The total solar thermal conversion efficiency is very close to the ideal absorber.The absorber has the ability of high conversion efficiency,spectral selectivity,broadband high absorption,polarization insensitive and wide-angle absorption.Its absorption property is the result of antireflection layer,cavity resonance and surface plasmon effect.Compared with previous studies,the device has higher photothermal conversion efficiency and better spectral selectivity.