Solar Cells, not quite an application of the photoelectric effect?

[frog1944]

Hi,

I was reading the dux college website on information for solar cells in ideas to implementations (https://dc.edu.au/hsc-physics-ideas-to-implementation/#Solar_cells_and_semiconductors), and it said the following "When photons hit a solar cell, its energy frees electron-hole pairs via the photoelectric effect (semiconductors are special, because visible light photons have enough energy to move electrons to the conduction band, not actually eject them like in early photoelectric experiments)."

If it's not like the photoelectric experiments, is it still the photoelectric effect?

Thanks

[jamonwindeyer]

Hey! Definitely is - It is the same mechanism that causes the emission of photoelectrons under normal circumstances. Even though it is not ejected we still attribute/group it to the same phenomenon

[frog1944]

Ok, thanks!

[bsdfjnlkasn]

Hey there,

Sorry to just chime in, but I thought that solar cells worked according to the photovoltaic effect (which explains why they're sometimes called photovoltaic devices. The photovoltaic effect is when a photovoltage is set up across the solar cell (result of charge separation during the formation of the p-n junction).

It differs from the photoelectric effect for the reason you specified, that the electrons aren't ejected completely outside of the material. The photoelectric effect can be observed in photocells.

Let me know if we need to be able to make this distinction for the HSC

[johnk21]

Hey there,

Sorry to just chime in, but I thought that solar cells worked according to the photovoltaic effect (which explains why they're sometimes called photovoltaic devices. The photovoltaic effect is when a photovoltage is set up across the solar cell (result of charge separation during the formation of the p-n junction).

It differs from the photoelectric effect for the reason you specified, that the electrons aren't ejected completely outside of the material. The photoelectric effect can be observed in photocells.

Let me know if we need to be able to make this distinction for the HSC

In regards to is the photovoltaic effect is correct, it certainly is. Not sure why there is two methods of explaining. However, i think it was in the 2010 or 2012 HSC there was a question on solar cells, and in the suggested answer the photoelectric effect was used. So because of this, I have opted to do it that way, but I do not see why you would be disadvantaged if you are using the photovoltaic effect, looks like a more complex and informative explanation anyways.

Edit: It was actually 2009 27c) This is the reccomended answer:
Question 27 (c)
Answers could include:
In the photoelectric effect light hits a material and electrons are released and are then able to produce a current. When light hits the n-type semiconductor photons hit electrons the light energy is transformed into energy for the electron. This energy frees the electrons by bridging the gap between the donor level and conduction band and also gives kinetic energy to the electrons, which produces a current in the solar cell.
When a junction is formed between the n-type and p-type semi conductor there is a potential difference set up between the n-type and p-type semiconductors at the junction. The electrons that move from n-type to p-type set up a positive potential in the n-type at the junction and a negative potential in the p-type. This potential can accelerate electrons across the field from the p- to n-type and prevents electrons from flowing from the n-type to p-type. This forces freed electrons from the n-type semiconductor to travel around the external circuit creating a current in the external circuit.