20_Engineering Solar Power 3080 Alexandra Walker

20_Engineering Solar Power 3080 Alexandra Walker - Near...

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Unformatted text preview: Near infrared to visible light Photodetectors are used to measure amount of light energy present Contains PN junction Light enters through the top Photons with greater energy than the bandgap create electron hole pairs E ph = hv E ph > E g E ph < E g Spectral cutoff at = 1.24/E ph Pairs are separated in depletion region Photocurrent is in reverse bias direction =forward bias current Direct and Indirect Band Gaps Conservation of energy and wave vector Direct bandgaps absorb light easier than indirect Indirect: Three particle collision: photon, phonon, and electron Absorption coefficient, Penetration Depth 1/ Low , penetration depth increases High , penetration depth is reduced and photons are absorbed closer to the surface Recombination increases High field in the depletion region Quicker response for carriers Short Circuit current is directly proportional to light intensity Open circuit voltage increases logarithmically with intensity We want Voc as large as possible for solar cells Comprised of photodetectors used to generate...
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20_Engineering Solar Power 3080 Alexandra Walker - Near...

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