Preparation And Optical Properties Of Silicon Nanostructure Arrays

Due to power generating costs higher than conventional fossil fuels,larger scale use of crystalline silicon solar cells is still limited.Micro-and nanostructured silicon——known as black silicon——is expected to solve this problem from two aspects.Black silicon has low reflectance over an extremely broad spectral range for quasi-omnidirectional incidence of light.Moreover,due to excellent light-trapping properties,black silicon might sustain a high light absorption,depite the solar cell thickness substantially reduce to below 100 ?m.While commercial solar cells currently have been fabricated on silicon substrates about 300 ?m in thickness,which is approximately half of the total manufacturing cost.In this dissertation,various Si nanostructure arrays,which were fabricated by nanosphere lithography(NSL)and subsequent metal-assisted chemical etching(MACE),have been investigated.To figure out Si nanostructure with relatively optimised antireflection performance,the optical properties of different Si nanostructure arrays were studied based on simulation and experimental results.The main contents focuse on the following aspects:(1)To realize precise control of the diameter of non-close-packed polystyrene sphere,the etching process of nanospheres in reactive ion etcher was thoroughly studied.Then,on the basis of NSL,on demand fabrication of Au nanohole arrays and controllable fabrication of the Au nanodisc arrays on the surface of Si substrate were realized by electron beam evaporation and magnetron sputtering technology.In the process of Au nanodisc arrays fabrication,a novel preparation method of Au nanoring array was realised.To figure out the mechanism of Au nano arrays formation,each step of the structure formation was studied in more detail.Finally,Au nanoring arrays with different period and size were realized.(2)On demand fabrication of Si nanowire arrays and controllable fabrication of Si nanohole arrays were realized by MACE,in which the prepared Au nanohole arrays and Au nanodisc arrays were used as respectively metal catalyst.In the MACE process,the influences of various parameters on etching results were analyzed and subsequently optimized.Then,the Au nanoring array was used as the etching catalyst to realize the fabrication of Si nanowire arrays initially.(3)The finite difference time domain(FDTD)method was used to simulate the optical properties of Si NWAs and Si NHAs with different diameters.The simulation results of optical properties were compared with the experimental data.For Si NWAs with length of ?m and period of 483 nm,the results show that Si NWAs with 300 nm in diameter have optimal antireflection performance.Due to the resonance absorption caused by eigenmodes excitation,Si NWAs sample with 100 nm in diameter is dark red;besides the absorption spectra in the wavelength of?570 nm appears an obvious absorption peaks in the simulation results of FDTD.For Si NHAs with length of 1 ?m and period of 483 nm,the results show that Si NWAs with 300 nm in diameter have optimal antireflection performance.Compared with 300 nm diameter Si NWAs,Si NHAs with 400 nm in diameter has better antireflection performance and is relatively optimal Si nanostructure.