A silicon cell thick has its external quantum efficiency measured at two wavelengths

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Earth, Climate & Energy Physics · Wave propagation and light in media

Energy from Physics, Ch The illuminated junction: generation, collection and the cell's characteristic

Problem

A silicon cell

180\,\mu\mathrm{m}

thick has its external quantum efficiency measured at two wavelengths. At

400\,\mathrm{nm}

the front surface reflects

R = 0.18

, the absorption length is

1/\alpha = 0.1\,\mu\mathrm{m}

and

\mathrm{EQE} = 0.58

. At

1000\,\mathrm{nm}

it reflects

R = 0.06

, the absorption length is

1/\alpha = 156\,\mu\mathrm{m}

and

\mathrm{EQE} = 0.40

. Take the rear as non-reflecting, so that light makes a single pass through the wafer. ((a)) At each wavelength find the fraction

A

of incident photons absorbed in the wafer, and the internal quantum efficiency. ((b)) Find the depth within which

99

per cent of the

400\,\mathrm{nm}

light entering the wafer is absorbed. ((c)) Split each incident photon stream into the fractions reflected, transmitted, absorbed but not collected, and collected. Name the largest loss at each wavelength, and say which of these losses passivating the front surface would reduce.

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