The correct movement of charge in PN junction

In summary, PV cells work by creating a potential difference at the junction between p-type and n-type materials, where photons with sufficient energy can excite electrons to the conduction band and drive them to the n-type side to be collected as current.
  • #1
Kidphysics
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Homework Statement



I've been reading and I just want to make sure that this is the correct way which pv cells work, I feel this is not correct. I want to find where I am wrong.

Once the p and n doped semiconductors are put together some carriers migrate and combine to form a depletion zone and have buildup of opposite ion charges. Now when a photon with enough energy hits an electron that is across the depletion zone (black photon) the photon has sufficient energy to cross the zone, following the electric field over to where the majority electron carriers are (we hope that it doesn't recombine with the positive holes) and if it successfully reaches the other side it flows across the wire?

Also I added the brown photon, I assume this ehp just gets recombined.

Homework Equations



http://pveducation.org/pvcdrom/solar-cell-operation/light-generated-current

edit* the red circle was an electron, so I believe my diagram is correct!

The Attempt at a Solution



http://imageshack.us/photo/my-images/854/pnjunction.png
tried to draw a diagram. Wouldn't mind drawing a few more so that I can understand fully.
 
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  • #2
Your diagram is correct.PV cells work by taking advantage of the potential difference created by the junction between p-type and n-type materials. When a photon with sufficient energy strikes the junction, it can excite an electron from the valence band to the conduction band. This electron is then driven by the electric field of the junction to the n-type side, where it can be collected as current. The holes left behind in the p-type side are driven to the opposite side of the junction. The brown photon is not used in the PV cell because it does not have enough energy to excite the electron to the conduction band. Instead, it just gets recombined with the holes in the p-type side.
 

1. What is a PN junction?

A PN junction is a type of semiconductor junction where a region of positive charge (P-type) meets a region of negative charge (N-type). This creates a depletion region, which is a barrier to the flow of charge.

2. Why is the correct movement of charge important in PN junctions?

The correct movement of charge is important in PN junctions because it determines the functionality of electronic devices. If charge does not move correctly, the device may not work as intended or may even be damaged.

3. How does charge move in a PN junction?

In a PN junction, charge moves through a process called diffusion. This is when particles move from an area of high concentration to an area of low concentration. In a PN junction, electrons from the N-type region diffuse into the P-type region, and holes from the P-type region diffuse into the N-type region.

4. What is the role of the electric field in the movement of charge in PN junctions?

The electric field is responsible for creating the depletion region in a PN junction. This region acts as a barrier to the flow of charge, allowing only a small amount of current to pass through. The electric field also helps to push the diffused charge carriers towards the opposite side of the junction.

5. How does the direction of current flow change in a PN junction?

The direction of current flow in a PN junction can change depending on the external voltage applied. In forward bias, the applied voltage reduces the size of the depletion region, allowing for a larger flow of current. In reverse bias, the applied voltage increases the size of the depletion region, restricting the flow of current.

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