Generation Mechanism of Inhomogeneous Minority Carrier Lifetime Distribution in High Quality mc-Si Wafers and the Impacts on Electrical Performance of Wafers and Solar Cells

To find out the causation of inhomogeneous minority carrier lifetime distribution in high quality multicrystalline silicon (mc-Si) wafers, impurities and lattice defects were systematically studied by means of Fourier transform infrared (FTIR) spectroscopy and metallography. Inhomogeneously distributed oxygen impurity and dislocations were demonstrated to be key leading factors, and the restriction mechanism was discussed. Scattering process caused by ionized impurities and dislocations decreased carrier mobility, while carrier concentration was not significantly affected. Measurements showed that resistivity was higher and more dispersive in low lifetime area. Solar cells were fabricated with these wafers. Cells' efficiency of inhomogeneous ones exhibited averagely 0.27% lower than the regular ones in absolute terms. Recombination centers and leakage loss induced by dislocations and impurities led to the reduction in shunt resistors and open-circuit voltage, and then affected the performance of cells.