FTIR Application In Crystalline Solar Cells

FTIR(Fourier Transform Infrared Spectroscopy)is an important characterization method used for determining the properties of semi-conductor materials.It has high impact on the characteriazation of unavoidable oxygen and carbon introduced by crystal growth and hydrogen and nitrogen introduced by the preparation of solar cells.Partial condensation of carbon and diffusion behavior in melting silicon of carbon of 1D solidification mc-silicon was studied.The behavior of oxygen precipitates during the preparation of large diameter CZ silicon solar cells was studied.The silicon nitride film deposited by tunnel PECVD(Plasma Enhanced Chemical Vapor Deposition)and plate PECVD was studied.The experiments show that,compared to axial oxygen concentration distribution in mc-silicon dependent on oxygen segregation and evaporation during the casting progress,the axial carbon concentration in 1D solidification mc-silicon used for solar cells agrees with segregation law.The axial carbon concentration in 1D solidification mc-silicon is well fitted by classical segregation reference.The effective segregation factor of samples is 0.45,which is much higher than the ideal.The diffusion velocity of samples is between 4.72x×10-88 cm/s and 4.7×10-7 cm/s according to BPS formula.It is much less than the standard solidification velocity during 1D solidification,around 3.125×10-4 cm/s.The results indicate that the carbon concentration of the useful ingots is hard to be decreased by decreasing the solidification velocity.The behavior of oxygen in large diameter CZ monocrystalline silicon was studied.The experiments show,as-grown oxygen precipitates existed in the large diameter CZ monocrystalline used for solar cells.The as-grown oxygen precipitates concentration of the head of the samples is 11.2 ppma,and the end is 12.4 ppma.The results indicate that,unlike the crystal growth of small diameter CZ monocrystalline silicon,the information of as grown oxygen precipitates is significantly promoted because of different kind of thermal field from small diameter's and larger crystal growth time.Simultaneously,the information principle of oxygen precipitates in the simulated thermal process of large diameter CZ monocrystalline silicon was studied.The experiments show there is no obvious change of oxygen concentration even the thermal annealing time is up to 16 hours.It indicates that there are almost no oxygen precipitates during the preparation of solar cells.Further,the efficiency of solar cells would not be obviously affected.In the end,the silicon nitride film deposited by tunnel PECVD and plate PECVD and their properties after thermal process is studied.The principle between as grown film and 750~850 ? thermal annealing process simulated solar cells procession is very similar.