Even though in a solar cell the N-type layer is negatively charged why do the electrons from the depletion layer get attracted to it?
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$\begingroup$ Because of the field in the depletion layer. $\endgroup$– Jon CusterCommented Apr 2, 2021 at 14:58
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$\begingroup$ @JonCuster What kind of field can you elaborate ? $\endgroup$– Vedansh TyagiCommented Apr 2, 2021 at 15:43
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$\begingroup$ The electric field that forms the depletion layer to bring the Fermi levels into alignment. This is pretty fundamental to the depletion layer and why it exists in the first place. $\endgroup$– Jon CusterCommented Apr 2, 2021 at 15:47
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$\begingroup$ But then why doesn't the depletion layer keeps on expanding, ie. what prevents the electrons in the N-type layer to fuse with the positively charged ions present near the boundary of the depletion layer and N-type layer. $\endgroup$– Vedansh TyagiCommented Apr 2, 2021 at 16:30
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$\begingroup$ Because the carriers have been brought into equilibrium. If you apply a reverse potential you can expand the depletion region, a common technique for detectors where you want more signal. But you need to go look at diode theory from the beginning - too long to answer in a comment. $\endgroup$– Jon CusterCommented Apr 2, 2021 at 17:03
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I think the main misunderstanding is that the n-layer is neutrally charged overall so it does not attract anything.
Only in the depletion region is there an electric field. The electric fields acts to sweep electrons towards the n-layer and holes toward the p-layer.
The depletion region partially overlaps both n and p doped layers. The part in the n-side is positively charged because the region is depleted of electrons which were once bound to the n-type dopants. This makes the n-side of the depletion region positive which attracts electrons towards the n-layer.
