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The dislocation dependence of open circuit voltage is studied based on Donolato's model for the effect of dislocations on minority carrier effective diffusion length [J. Appl. Phys. 84, 2656 (1998)]. Experimental data measured on thin-film solar cells show a strong decrease of open circuit voltage V-oc with an increase in defect density. The analysis of the recombination currents indicates that V-oc is largely reduced by space charge region recombination. For a quantitative study on the relationship between dislocation density, effective diffusion length, and V-oc the data are fitted with an extended version of Donolato's model. Taking into account the base recombination current as well as the space charge region recombination current, the modeled curves fit very well to the experimental data. However, satisfactory fitting results require that the region of high recombination is set wider than the "effective depletion region width," which is calculated from the electrical field strength in a planar p-n junction. This effect can be explained with the assumption of a geometrical enlargement of the p-n junction due to defects like dislocations

In 1998, Donolato presented an analytical model describing the effect of dislocation density on minority carrier effective diffusion length [J. Appl. Phys. 84, 2656 (1998)]. While this analysis was derived for a "semi-infinite" specimen, our objective is the appropriate description of thin devices, such as wafer or thin-film based crystalline Si solar cells with back surface field or passivating layer on the rear side. Therefore, Donolato's model is extended for specimen of finite thickness and finite recombination velocity at the back surface. Since the associated boundary value problem does not allow a straightforward analytical solution, we derive an approximate expression, which is validated by numerical simulations. In the original work, Donolato uses a special definition of an "effective diffusion length." This definition is different from the quantity usually referred to as effective diffusion length when analyzing quantum efficiency data. Furthermore, Donolato's definition does not refer to the typical operation conditions of a solar cell. We therefore modify Donolato's model for the effect of dislocations consistently using the quantum efficiency effective diffusion length. Finally, our model is applied to the determination of dislocation recombination strength in thin-film solar cells with back surface field from effective diffusion length maps

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