Reduction of the apparent shunt resistance effect in silicon concentrator solar cells

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Abstract
Silicon solar cells of lowly doped base, under concentration, show a slope in the low voltage region. the slope varies with the irradiance and is similar in some aspects to that caused by a shunt resistance. This apparent shunt resistance reduces the fill factor and the efficiency. In consequence, such cells cannot operate effectively at concentrations above 20 suns.Actually, this apparent shunt resistance is due to the transition from low to high injection in the cell base. This is confirmed by an accurate simulation using the PC1D code. A semi‐quantitative model of the mechanism is developed. It is shown that by thinning the cells the mechanism is strongly reduced. Thin cells are fabricated virtually free of low voltage slope at concentrations of 80 suns.Also, the existing short‐circuit current sub‐linearity is avoided in the thinned cells.