Oxygen And Carbon Impurities And Defects In Crystalline Silicon For Solar Cells

As an inexhaustible and clean renewable energy, the solar energy has drawn extensive attention recent years. However, the large-scale application of silicon solar cells are impeded due to a higher cost. As we know, the improvement of the cell efficiency is one of important strategies for the reduction in cost. The light element with high content such as oxygen and carbon are inevitable impurities in silicon crystals, which seriously affected the performance of silicon solar cells. Therefore, it is extremely necessary to study the properties of impurities and defects for the photovoltaic development.In this work, we have studied the effect of oxygen precipitation on the performance of silicon solar cells and the behaviors of vacancies-oxygen-related in neutron-irradiation crystalline silicon. Besides, the properties of IR absorption band located at 1207 cm-1 at room temperature observed in some silicon wafers has been investigated. The main results are summarized as follows,(1) The oxygen precipitation effectively act as a recombination center in silicon wafers. The open-circuit voltage and the short-circuit current of solar cells both become smaller because of the presence of oxygen precipitates.(2) The elimination activation energies of VO complex in Gallium (Ga)-doped (CZ) silicon and Gallium and Germani)μm(Ge) co-doped(GCZ) silicon are.89 eV and 2.29 eV and the generation activation energies of VO2 complex are 1.69 eV and 1.52 eV. respectively. The infrared results at 10K show the metastable 0-V-O complex are formed during annealing at 220-250℃in GCZ silicon wafers and the activation energy for the formation of 0-V-O complexes is about 0.48 eV. which is much lower than that of the formation of stable configuration VO2 complexes.(3) An infrared absorption band at 1207 cm-1 can be newly observed in the case of carbon content being above 1.7X1O17 cm*"\Moreover, the intensity of this band increases with an increase of carbon concentration in silicon crystal, suggesting the 1207 cm-1 might be related to carbon-related defect in silicon crystals.