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Line 88: + − + − + + + + − + − − An electron hole pair is created, i.e a free electron and a free hole. Because of the existing electric field at the depletion Zone, this freed electron is attracted to the n-type side, being repelled by the barrier. Likewise, the holes encounter is attracted to the p-type side. − [[File:PV cell with photon and electron holes 2.png|left|thumb]] − Now what? The electrons and holes are free and excited with nowhere to go. The continual incident rays of the photons continue to generate electron hole pairs and charge separation causes the presence of uncombined excess negative charges on the n-type side and excess holes on the p-type side, a charge imbalance exists in the cell. − [[File:PV cell in circuit.png|left|thumb|375x375px]] − If we then connect the n-type side to the p-type side of the cell by means of an external electric circuit, current flows through the circuit (which responds just as if powered by a battery} because this reduces the light induced charge imbalance in the cell. + + + − + + − + − − [[File:PV cell in circuit 3.png|left|thumb|379x379px]] − −
Update
[[File:PV effect 3.png|thumb|alt=|left|3. Potential barriers when all electrons have filled holes and are now electrically stable]]
[[File:PV effect 3.png|thumb|alt=|left|3. Potential barriers when all electrons have filled holes and are now electrically stable]]
[[File:PV effect 4.png|thumb|alt=|4. Depletion zone of a PN junction]]
[[File:PV effect 4.png|thumb|alt=|4. Depletion zone of a PN junction]]
This process continues back and forth until the number of electrons which have crossed the junction have a large enough electrical charge to repel or prevent any more charge carriers from crossing over the junction. Eventually a state of equilibrium will occur producing a '''“potential barrier”''' zone around the area of the junction as the donor atoms repel the holes and the acceptor atoms repel the electrons.
This process continues back and forth until the number of electrons which have crossed the junction have a large enough electrical charge to repel or prevent any more charge carriers from crossing over the junction. Eventually a state of equilibrium will occur producing a '''“potential barrier”''' zone around the area of the junction as the donor atoms repel the holes and the acceptor atoms repel the electrons.
Since no free charge carriers can rest in a position where there is a potential barrier, the regions on either sides of the junction now become completely depleted of any more free carriers in comparison to the N and P type materials further away from the junction. This zone around the '''PN Junction''' is now called the '''Depletion''' Layer.
Since no free charge carriers can rest in a position where there is a potential barrier, the regions on either sides of the junction now become completely depleted of any more free carriers in comparison to the N and P type materials further away from the junction. This zone around the '''PN Junction''' is now called the '''Depletion''' Layer.
As the N-type material has lost electrons and the P-type has lost holes, the N-type material has become positive with respect to the P-type which has also turned negative.
As the N-type material has lost electrons and the P-type has lost holes, the N-type material has become positive with respect to the P-type which has also turned negative.
[[File:PV effect 6.png|thumb|alt=|center]]
[[File:PV effect 6.png|thumb|alt=|center|349x349px]]
==== Generating current with Photons ====
==== Generating current with Photons ====
Now that we understand the concept of depletion layer and the electric field generated, we now represent this basic diode form in the normal way a PV module was created :
Now that we understand the concept of depletion layer and the electric field generated, we now represent this basic diode form in the normal way a PV module was created :
[[File:PV effect current.png|thumb|alt=|306x306px]][[File:PV effect 6ok.png|center|thumb|alt=|365x365px|Structure of a PV cell]]How then is the electric current generated ?When sunlight or energy from the light (Photons, that has enough energy to free an electron from a bond in the silicon crystal) strikes the PV cell, and is absorbed by the semiconductor in the depletion zone.
[[File:PV effect current.png|thumb|alt=|306x306px]][[File:PV effect 6ok.png|center|thumb|alt=|365x365px|Structure of a PV cell with the PN junction and depletion zone]]
How then is the electric current generated ?
[[File:PV cell with photon.png|left|thumb|314x314px]]
[[File:PV cell with photon.png|left|thumb|314x314px]]
[[File:PV cell with photon inside.png|center|thumb|342x342px]]
[[File:PV cell with photon inside.png|thumb|352x352px|alt=]]When sunlight or energy from the light (Photons, that has enough energy to free an electron from a bond in the silicon crystal) strikes the PV cell, and is absorbed by the semiconductor in the depletion zone.[[File:PV cell with photon and electron holes.png|left|thumb]]
[[File:PV cell with photon and electron holes.png|left|thumb]]
An electron hole pair is created, i.e a free electron and a free hole. Because of the existing electric field at the depletion Zone, this freed electron is attracted to the n-type side, being repelled by the barrier. Likewise, the holes encounter is attracted to the p-type side.
[[File:PV cell with photon and electron holes 2.png|left|thumb]]
Now what? The electrons and holes are free and excited with nowhere to go. The continual incident rays of the photons continue to generate electron hole pairs and charge separation causes the presence of uncombined excess negative charges on the n-type side and excess holes on the p-type side, a charge imbalance exists in the cell.
[[File:PV cell in circuit 2.png|left|thumb|378x378px]]
[[File:PV cell in circuit.png|left|thumb|350x350px]]
If we then connect the n-type side to the p-type side of the cell by means of an external electric circuit, current flows through the circuit (which responds just as if powered by a battery} because this reduces the light induced charge imbalance in the cell.
Negative charges flow out of the electrode on the n-type side, through a load (such as a light bulb}, and perform useful work on that load (such as heating the light bulb's filament to incandescence}. The electrons then flow into the p-type side, where they recombine with holes near the electrode.
Negative charges flow out of the electrode on the n-type side, through a load (such as a light bulb}, and perform useful work on that load (such as heating the light bulb's filament to incandescence}. The electrons then flow into the p-type side, where they recombine with holes near the electrode.
The light energy originally absorbed by the electrons is used up while the electrons power the external circuit. Thus, an equilibrium is maintained.
[[File:PV cell in circuit 3.png|thumb|350x350px|alt=]][[File:PV cell in circuit 2.png|thumb|351x351px|alt=|center]]The light energy originally absorbed by the electrons is used up while the electrons power the external circuit. Thus, an equilibrium is maintained.
The incident light continually creates more electron-hole pairs and, thereby, more charge imbalance; the charge imbalance is relieved by the current, which gives up energy in performing work. The amount of light incident on the cell creates a near proportional amount of current.
The incident light continually creates more electron-hole pairs and, thereby, more charge imbalance; the charge imbalance is relieved by the current, which gives up energy in performing work. The amount of light incident on the cell creates a near proportional amount of current.
And that is the photo-voltaic effect, a work coined from “'''photo'''” with the Greek '''meaning light''' and “voltaic” '''meaning''' voltage.
And that is the photo-voltaic effect, a work coined from “'''photo'''” with the Greek '''meaning light''' and “voltaic” '''meaning''' voltage.
== References & Videos ==
== References & Videos ==