Design of antireflective coatings for AZO low infrared emissivity layer

In this letter, we investigate the structural, optical, and electrical properties of Al-doped ZnO （AZO） thin film coating prepared by direct current （DC） facing-target sputtering method at room temperature, of which the average optical transmittance is 81% between 400 and 700 nm while the sheet resistance is about 10 Ω/□. Then, based on this AZO coating, in order to enhance the transmittance, interfacial adhesion strength and weathering resistance, two kinds of antireflective coatings are designed for different application purposes. For the two kinds, the highest transmittances in the visible region （400 700 nm） can reach 86.9% and 81.8%. resoectivelv. The design is performed using Macleod Optical Design software.     

New criterion for optimization of solar selective absorber coatings

We discuss a merit function F as judgment of photo-thermal conversion efficiency instead of two indepen- dent parameters： solar absorptance α and thermal emittance ε. The merit function F is developed using Essential Macleod software to optimize the photo-thermal conversion efficiency of solar selective coating. Bruggeman and Maxwell-Garnett models are used to calculate the dielectric function of composite cermet film. Mo, W, V, and Pd are used as metallic component as well as infrared （IR） refector materials, and SiO2, A1203, A1N, and TiO2 are used for dielectric component or antireflection （AR） layer materials. The layer structure can be described as substrate （Sub）/IR reflector/ high-metal-volume fraction （HMVF）/ low-metal-volume fraction （LMVF）/AR. Results show that Mo-Al2O3, Mo-AlN, W-SiO2, W-A12O3, V- SiO2, and V-A1203 double-cermet coatings have high conversion efficiency which is greater than 86%. The best among above is Mo-SiO2 with α=0.94, e=0.05 at 450℃, f= 89.9%. Some selective coatings with different layer thicknesses have been successfully optimized for different solar irradiations （air mass （AM0）, AM1.5D, and AM1.5G spectra） and different operating temperatures （300, 450, and 600 ℃）, respectively. However, the optical constants for calculation are from the software, most datum are measured for bulk materials. Therefore. results are more useful to indicate the trend than the exact values.