Design And Fabrication Of Solar Selective Absorption Films Based On Photonic Crystals

The development of solar selective absorbing films is the key to improving the photothermal conversion efficiency in solar energy collector technology.In order to meet the spectral selectivity requirements of solar absorbing films,we use the bandgap structure and flexible spectral design of one-dimensional photonic crystals to regulate and optimize the transmission characteristics of light waves in the range of 0.4mm²0mm.A new method for designing and realizing the high-absorption in the visible-near infrared region and high reflection in mid-far infrared region film was explored.From the basic requirements of the application of solar selective absorbing film and the theory of photonic crystal design,one-dimensional photonic crystal structure absorption film Al/Si₃N₄/?Ti/Si₃N₄?^N?N is the number of cycles?was designed,and the influence of the film structure parameters on its reflection and transmittion was calculated using the transmission matrix method.The results show that when the number of cycles N is 2,the absorption of the film in the visible-near infrared region is as high as 94%,and the average reflectance in the middle-far infrared wavelength is 7%.Comparing to the existing absorption film it has better heat absorption and heat storage performance;for solar oblique incidence,when the incident angle is not more than 60°,the film maintains about 80%absorption rate for s-polarized light,and the incident angle is not greater than At 75°,the p-polarized light can maintain an absorption rate of more than 90%.Al/Si₃N₄/?Ti/Si₃N₄?² films with structural parameters were prepared on silicon substrates by magnetron sputtering and chemical vapor deposition techniques,and their microstructure,reflectivity and thermal stability were analyzed.The results show that the thickness of Si₃N₄,Ti,and Al unit layers of the absorber films are 67.4nm,23.6nm,and80.9nm,respectively.The visible-near infrared absorption reaches about 92%,and the middle-far infrared reflectance is over 90%.The performance indicators are more consistent.In addition,the absorption film was annealed at a high temperature of 600?for 2 hours,and its spectral characteristics were substantially maintained,reflecting that the absorption film has a high thermal stability.