A simplified expression for optical absorbance in Si solar cells

An expression for optical absorbance in Si is derived, which is a simplification of the expression for the same quantity given by Basore. Unlike the Basore expression, the simplified expression does not require the determination of the front-surface external and internal reflectance prior to be used. For textured solar cells it is equivalent to the Basore expression, if the average ray-path angle with respect to the surface normal is equal at all passes of light across a cell. Unlike the Basore expression, it allows fitting the measured quantum efficiency of planar solar cells with diffuse rear surface. The simplified expression can be easily implemented in the numerical simulation program PC1d. The measured quantum efficiency of a textured solar cell is fitted with both the new and Basore expressions. Overlapping fit-curves are obtained. The measured quantum efficiency of a planar solar cell with not-polished rear surface is fitted by using the new expression. Finally, with the new expression, the maximum absorbance for weakly absorbed light is estimated in solar cells with textured back surface at both flat and textured front surfaces.