Enhanced Optical Absorption And Luminescence Of Films By Localized Surface Plasmon

There is huge potential for solar energy in solving global energy crisis and slowing down global warming.As the most basic material in semiconductor industries, silicon has many advantages for solar cells such as high reserves,mature technology, high efficiency and stability.Amorphous silicon thin-film solar cells,compared to single crystal and polycrystalline silicon solar cells,enjoy many outstanding advantages,such as lighter weight,larger optical absorption coefficient,better anti-radiation performance,lower cost and so on.However,since the optical band gap of amorphous silicon is approximate 1.7 eV,it results the small optical absorption coefficient at large wavelengths of solar radiation spectrum,as well as low photoelectric conversion efficiency.In addition,it is difficult to reduce the cost by further decreasing film thickness because the carrier diffusion length of amorphous silicon is just about 100 nm,which seriously affects the silicon photovoltaic market in the popularization and application.Then using surface plasmon to enhance the efficiency of amorphous silicon thin-film solar cells has become a hot topic in recent years.Evidentsly,using surface plasmon to enhance light absorption is expected to find wide potential applications in solar cells.In this thesis,metal nanoparticles were produced,and the factors that affect the morphology and suface palsmon resonance properties of metal particles were investigated.Then we used the suface palsmon of Ag nanostructures to increase the optical absorption efficiency of a-Si films.Finally,we used the suface palsmon of Ag nanostructures to increase the light emission of Y₂O₃:Yb³⁺ films.The primary significant results were follows:(1) Ag nanoparticles were prepared by electron beam evaporation.We found the morphology and surface plasmon of Ag nanoparticles dependent on temperature.And Subsequent thermal processing could change the morphology of Ag nanoparticles and tune the surface plasmon resonance wavelength.And with different dielectric materials around the Ag nanoparticles,surface plasmon of Ag nanoparticles could be tunned.(2) By adjusting the size of Ag nanoparticles,the optical absorption of a-Si thin film solar cells can be optimized.The average reflection value of a-Si films for the long wavelength range of optical spectra is reduced by evaporating Ag nanoparticles onto the a-Si films.(3) The photoluminescence of Y₂O₃:Yb³⁺ films was enhanced by coupling with surface plasmon of Ag nanoparticles and the mechanism was investigated.The results show that photoluminescence enhancement resulted from the enhancement of excitation efficiency.And it was found that the photoluminescne enhancement is related to the Ag nanoparticles size.