An accurate solution for the dark diffusion current of preferentially doped polysilicon solar cells

Abstract

The total dark diffusion current of a preferentially doped polysilicon solar cell along the grain boundaries cannot be derived easily. Using the Green's function method and the moment method, the expressions for the dark currents of the horizontal and vertical junctions of an elementary cell are well established. The preferential doping realizes vertical junctions along the grain boundaries and at the same time decreases the total dark diffusion current of the cell. Consequently, this allows an enhancement of the cell efficiency. In fact, the results show that in the case of a cell of small width ( W = 20 μm), the preferential doping with a penetration depth of ( Z d = 15 μm) decreases the dark diffusion current of the cell by about 63%. However, the enhancement of the cell efficiency which resulted does not exceed 0.77%.