Mechanism And Craft Control Research Of Poly-Si Films By Aluminmum-induced Crystallization Amorphous Silicon For Thin-film Solar Cells

With the concept of sustainable development and environmental protection deeply rooting among the people and gradual exhaustion of ordinary petrifaction energy sources,photovoltage(PV)technology is gaining increasing interest again. Crystallization silicon(c-Si)solar cells,with high efficiency and stable performance, starve for the substitute technology due to the expensive cost and hard pollution for fabrication of silicon wafer.Poly-Si thin-film solar cells maybe one of an alternative and promising way to reduce cost of solar cell of silicon wafer.The theses emphasize the fabrication technology of polycrystalline thin-films of solar cell,and make research on the aluminum-induced crystallization(AIC),a promising preparation method for poly-Si thin-film at low temperature.Glass/Al/a-Si composite layer was deposited using dc-magnetron sputtering,and fabricated the poly-Si thin-film by AIC;studied the influence of process parameters on structure and performance of poly-Si thin film;the initial stage of the aluminium-induced layer-exchange(ALILE)process was studied theoretically; decreasing the annealing temperature for AIC and a route to getting low Al dopant concentration poly-Si thin film were focused on.1,The experiments of aliminmum-induced crystallization of amouphous silicon were systemly studied.We have done a series of experiments to discuss the influcence of experimental parameters such as annealing teimperature,annealing time,and thickness of aluminmum films,buffer layer(Al₂O₃),annealing atmosphere,and fabric of substrate.The results showed that,that parameters are play a mulriple role in annealing process and properties of fabricated poly-Si films.So,for getting a high electronic quality poly-Si thin films,above parameters should be optimized and fitted together.2,The initial stage of the aluminium-induced layer-exchange(ALILE)process is studied theoretically.The diffusion of silicon atoms from an amorphous Si layer into an Al layer through a buffer layer(Al₂O₃)prior to Si grain nucleation within the Al layer is considered.A kinetic model is devoted to describe this process.Based on the framework of this model,the evolution of the Si concentration within the Al layer prior to Si grain nucleation and the nucleation time are investigated for different annealing temperatures and preparation conditions of the buffer layer.From the comparison of results of calculations with experimental data,the activation energy (E_A)of 0.57 eV for a-Si atom diffusion into Al film was determined,which maybe the reason for crystallization of a-Si at low temperature(＜577℃)by AIC.3,Polycrystalline silicon(poly-Si)thin-film is fabricated on Al-coated planar glass substrates at the temperature below 100℃,using AIC amorphous silicon(a-Si) deposited by dc-magnetron sputtering under an electric field.The properties of NA poly-Si films(AIC of dc-magnetron sputtered silicon non-annealing)are characterized by Raman spectroscopy and x-ray diffraction(XRD)spectroscopy.A narrow and symmetrical Raman peak at a wave number of about 521 cm^-1is observed for samples,showing that the films are fully crystallized.XRD spectra reveal that the films are preferentially(111)oriented.Furthermore,the XRD spectrum of the sample prepared without electric field does not show any XRD peaks for poly-Si,which only appears at about 38°for Al(111)orientation.It is indicated that the electric field plays an important role in crystallization of poly-Si during the dc-magnetron sputtering.Thus,high quality poly-Si film can be obtainedat low temperature and separate post-deposition step of AIC of a-silicon can be avoided.24,Typically,highly p-doped(2×10¹⁸cm^-3)poly-Si films fabricated by the aluminuminduced layer exchange(ALILE)process are not suitable as solar cell absorber layers.In the thesis,the fabrication of high-quality,continuous polycrystalline silicon(poly-Si)films with lower doping concentrations(2×10¹⁶cm^-3) using AIC is reported.Secondary-ion-mass spectroscopy(SIMS)results show that annealing at different temperature profiles leads to a variety of Al concentrations.Hall Effect measurements revealed that Al dopant concentration depends on the annealing temperature and temperature profile.Raman spectral analysis revealed that samples prepared via AIC contain some regions with small grains.