Modelling of the influence of dislocations on effective diffusion length and photocurrent of polycrystalline silicon cells

Abstract

Green's function is used to establish a three-dimensional model to obtain a detailed rigorous analytical expression of the effect of dislocations. The predictions of the model were verified by measuring the photocurrent, the spectral response, and the effective diffusion lengths of minority carriers (L/sub eff/) and by evaluating the dislocation etch pit density. Three materials are considered, POLYX, SILSO, and SEMIX, which differ by the value of the diffusion length (L/sub n/) in the homogeneous regions of the bulk. It is found that the values of J/sub sc/ and L/sub eff/ are dependent on N/sub dis/ and S/sub d/ provided they are greater than 10/sup 4/ cm/sup -2/ and 10/sup 4/ cm-s/sup -1/, respectively. The computed variations also depend on the value of the diffusion length in the homogeneous region of the bulk material. A reasonable agreement is found with experimental results obtained with large-grained polycrystalline materials such as SILSO and POLYX.<>