photoelectric/photovoltaic?? (1 Viewer)

[booboo]

what is the relationship between photoelectric effect and photovoltaic effect??

 

[1234567]

there is a photovoltaic effect???

should be the same......
since photoelectric effect is applied to make photovoltaic cells. so it should be just anothe rway of saying it.......a very fancy way.......

 

[Horndog]

photo voltaic/electric

The photoelectric effect is the effect of an electric being displaced be a photon of a particular frequency, there is no photovoltaic effect - you are thinking of a photovoltaic cell which utilyses the photelectric effect to convert light energy to electrical energy, Eg a solar cell is a photovoltaic cell.

 

[Wintermute]

No. The photoelectric effect is when an electron is knocked clean off the surface of a metal by a photon. The photovoltaic effect is when an electron is lifted into the conduction band of a semiconductor by a photon.

 

[1234567]

so...photovoltaic......under influence of light, electron goes to conduction band and thus creates current? (do they create current or voltage?)
photoelectric, just simply electron being knocked off by uv light...?

 

[BlackJack]

PV: They create both. The movement of electrons also creates voltage, and vice versa.
But there is no net potential difference, as electrons move around the circuit to cancel the voltage created in opposite ends of the cell.

edit: This prob. should be clarified... the PV cell is now like a battery.

PE: Yep..

 

[1234567]

sorry, i m really confused about directions of current and voltages.
can u explain?

 

[BlackJack]

Cell, initially:

P-type
--------
N-type

When these two are together, some of the exta electrons flow from the N-type to the P-type to satisfy the 4 bonds to each atom...

P-type (-'vely charged)
------ (e- goes up to fill in lattice holes)
N-type (+'vely charged)

When light comes in... it knocks the e- into the conduction band...
It flows to the N-type, which attracts the e- with its positve charge.

Electron flow is P-N INSIDE THE CELL
Hole flow is N-P INSIDE THE CELL
[lights!]
P-type (now less -'ve)
------ (e- goes down, attracted to the +'ve charge)
N-type (now less +'ve)


Potential difference is created, where the N-type is -'ve, P is the +'ve end.
Connect this to the outer ciruit and electrons will flow around from the N-side, through the ciruit, to the P-side. (conventional current the other way)

 

[kaseita]

note that his talking about the junction, where the P and N types meet, not the whole thing. So around the point where they meet, positive holes from the P will move to the N, and electrons from the N to the P, to fill up the gaps.
However the majority of the N type silicon remains negatively charged, and the P type silicon, positively charged.
This has the effect of creating a potential difference across the junction, so when an electron is freed by light from the N type, it can't go straight to the P type through the junction, since at the junction, the P type is negatively charged.
so to get to the P type, the electrons have to go through the external circuit to get to the P type. Then the electron is able to return back to the N type, through the junction.
I think that's what I found the most difficult thing understanding.

 

[The Spruce Moose]

spot on black jack thats wat i thought but i only scored 51 in the catholic trial sooooo im pretty stupid