Perimeter recombination in thin film solar cells
Surface recombination has a profound effect on the performance of a solar cell, at the illuminated surface reduces its photocurrent and along the cell's perimeter increases its dark current. The perimeter recombination current has two components; the first is due to recombination at the surface that intersects the space-charge layer while the second originates from recombination at the surface of quasi-neutral regions. The current due to recombination at the depleted layer surface is treated in a similar way to that of the bulk, using a simple model. We present an analytical form that produces results that agree well with reported experimental findings. The recombination current outside the space-charge region is of two-dimensional nature, it represents lateral diffusion of minority carriers from the boundary of the depleted layer to the perimeter. This current is calculated by solving numerically a two-dimensional continuity equation. As the ratio of perimeter to area is increased the perimeter current acquires important proportions, consequently the expected bulk recombination current becomes insignificant.
KeywordsSolar cell MEMS Surface recombination