Performance Study And Film Design Of Solar Film Relfective Materials With High Reflectance

Solar energy, as a renewable energy source, has attracted an increasing interest as ameasure to resolve worldwide energy shortages and to overcome environmental problems.Solar power generation consist of concentrating solar power（CSP） and solarphotovoltaics（PV）. Light and heat concentrating collector, mirror drive and tracking systemsare core equipments for CSP. Moreover, the concentrating systems including heliostat and suntracking device cost more than50%of the total investment number. The solar reflectivematerials in condenser systems have been widely used in middle-high temperature applicationsystems and concentrating PV systems, thus the quality of reflective materials directlydetermine the conversion efficiency of solar PV cells and the cost of CSP. High-reflectancematerial is therefore critical to improve the utilization of solar energy.Silver and Aluminum thin films deposited on glass substrate were prepared by directcurrent （DC） magnetron sputtering and SiO₂films were prepared by radio frequency （RF）magnetron sputtering on their surface as a protective layer. Reflectance spectra of films wereobtained using UV-VIS-NIR spectrophotometer. The visible light range is from380to780nmand the sunlight range is from300to2500nm. Besides, this thesis designed and simulated thereflective thin films of Ag-SiO₂and Al-SiO2using Essential Macleod optical coating designsoftware. Furthermore, thin film materials for abrasion resistance, adhesion, resistance toaging experiments and annealing treatment were studied. The results showed that thereflectance curves of Ag-SiO₂and Al-SiO₂films were cyclically changed, and the optimalthickness of silver film is about130nm, and the SiO₂film with thickness of320nm and400nm on a silver surface serves as a good protection film and aging resistance without seriousdegradation of reflectance, the solar reflectance and light reflectance of this films can reach to96.66%and98.84%, respectively. The adhesion between silver and glass substrate becamestronger when a plus transition layer of copper was added in. Through experiments, annealingis an effective measure to improve the reflectance of these films, and the reflectance of thefilm annealed at350℃in vacuum is the highest. With the increase of the annealingtemperature, the reflectance declined slightly, but was higher than that of the unannealed film.Furthermore, the reflectance of the films annealed below250℃in air improved to some extent, but they declined obviously and even worse than the unannealed ones when theannealing temperature exceeds300℃.The appropriated thickness of the films were chosen as50nm for Al film and230nm forSiO2film, respectively. The solar reflectance reach to89.50%. In this case, the calculatedvalue of the reflectance are basically consistent with the experimental value. It was found thatthe reflectance of Al film has been reduced because of the Al₂O₃film formed by oxidation ofitself if there are no other protective layers. Besides, the reflectance decreases as the filmthickness of Al₂O₃increases within70nm. Particularly, the solar reflectance decreasesslightly from91.13%to88.41%when its thickness increase from0to30nm.Finally, we designed and prepared a film of Glass/Ag（130nm）+SiO₂（400nm）+TiO₂/Air,then explored the preparation process of TiO₂and the influence upon film hydrophilicity afterannealing treatment.