Rear illumination

Illuminating the cell through the back achieves a higher sensitivity to the back surface recombination than illumination through the front surface. Obviously, the cell has to be bifacially sensitive to permit rear illumination. The quantum efficiency for back illumi­nation is [409, 410]

IQE =———————- A——————– (C.9)

cosh(^/I) + -^-sinh(^os/I)

Here, plotting IQE versus La yields a linear relation. The slope and intercept provide information on Sb and L. Equation (C.9) predicts that the ratio of the slope to the inter­cept is Sb/Dn; here Dn is the diffusion coefficient of the minority carriers (electrons).

Подпись: Figure C.5. The inverse internal quantum efficiency is linear in the optical absorption length. For absorption lengths greater than the cell thickness the linear relation does not hold.

C.3 Effective diffusion lengths (formulas)

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