Influence of defects and impurities on solar cell performance
Department of Electrical and Computer Engineering
Doctor of Philosophy
Ravindra, N. M.
Sopori, Bhushan L.
Defects on solar cells
Multicrystalline silicon (mc-Si) solar cells exhibit high impurity content and higher density of crystal defects such as grain boundaries, dislocations, stacking faults and impurity precipitates. Even though the effect of dislocations on mc-Si solar cell performance has been studied, a severe lack of understanding of the quantitative effects of dislocations on cell parameters still exists. Some correlation has been reported under the assumption of a uniform distribution of dislocation density and a negligible effect of front and back surface recombination velocity. This assumption can cause a significant error as the current mc-Si technology provides good surface passivation by SiN:H and very effective back surface fields.
This work is an extension of previous models that use Green Function to include the influence of front (S1) and back (S2) surface recombination velocities. The three dimensional continuity equation of the minority carriers has been solved in a solar cell having periodic array of dislocations and with front and back surface recombination. Each dislocation is considered to be a space charge cylinder perpendicular to the surface and extending through the entire cell. The calculations show that low dislocation densities (< 104 cm-2) have very little effect on the cell performance. This is in agreement with the previously published data. The results of calculated dependencies of cell parameters on the dislocation density for different recombination activities are discussed in this work.
njit-etd2012-007 (131 pages ~ 2,775 KB pdf)
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Created June 27, 2012