Tutorial: Solar Cell Operation
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- čas přidán 5. 09. 2024
- MIT 2.627 Fundamentals of Photovoltaics, Fall 2011
View the complete course: ocw.mit.edu/2-6...
Instructor: Joe Sullivan
This video summarizes how a solar cell turns light-generated mobile charges into electricity, highlighting the cell's physical structure with layers with different dopants, and the roles of electric fields and diffusion of holes and electrons.
License: Creative Commons BY-NC-SA
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Best fundamental description of Solar Cell operation I've ever seen. Much appreciated Joe and MIT.
To avoid confusion, wouldn't it be better to demonstrate the electron-hole pair being generated in the p-type silicon (right-hand-side) and the excess electron being swept by the electric field? (at 4:28)
Best explanation I’ve come across, and the only one that made me truly understand this. Thank you.
And this is why MIT is the best tech university in the world. I've seen this animation and explanation 20 times explained on CZcams, at universities but they never were able to actually explain it right and in detail. Here they're able to not only nail the explanation, they were able to do this in practice themselves and actually did it and demonstrated it. Same quality that I've seen from CS50 at Harvard, very nice.
I agree though with the other commenter, would be cool to be see the doping process.
I see quite a mistake in this explanation. Keep in mind that the extrinsic semiconductors do have majority as well as minority charge carrier. If the light shines on one side of semiconductor say N-type free electrons and holes are generated , the freed electrons moves randomly and collides with some random holes residing in the same semiconductor block and vanishes producing no current. Its the PN junction upon which if the light energy is incident creates useful current because the electrons and hole pairs generated in the junction are pulled apart by the electric field build in the junction toward the opposite poles.
It would be very interesting to see the doping process applied in the lab.
Only this video explains why electrons should travel the outer circuit. Awesome and thank you dear fellow.
This is fantastic! Well done! Exactly what I wanted to see!
Thanks Joe Sullivan for your clear explanation
Best video on solar cell on entire CZcams. Loved it 💙💙💙
I never seen this type of lecturer in my life..
best video about how these work that I've seen.
absolutely beautiful, simple and neat explanation
you are the most genius I have ever seen.
If I have the chance to study at MIT, I definitely would!
Thank you!
Joe, you are amazing!
Your video saved my project's life!! Thanks a lot!!!
Thanks man! This cleared my major doubts!
Akash Singh Correct me if I am wrong, but how good the cell can perform depends on the rate of electron-hole pair generation, not the amount of free electrons under no-light. The cell simply reach the equilibrium point and no current is generated.
i really do appreciate this work , i haven't seen anyone doing such a great work , the only problem is that u have mistaken at B- the hole in the Boron is going to be replaced by an electron from a neigbhor silicon atome due to the ambient temperature then we are going to get the negatif charge of the Boron thanks for correcting it , getting deep in the physics beneeth this phenomenon makes it confusing , i agree to everything u said but the boron won't get the negatif charge to become B- tell it'll get a new electron from a nieghbor silicon and this silicon atome is going to become a positif charge due to the fact that it lost an electron , thank you for this amazing work
Absolutely well done and definitely keep it up!!! 👍👍👍👍👍
Jazak Allah Khira
Awesome explanation!
Thanks.
Very well done.
requesting to acess dr lewin videos.
On the "hole-y" side when a silicon atom is struck by a photon I assume the electron would flow the other way, but would this movement temporarily slow the flow, due to any E-m interactions?
A VERY GOOD INFORMATIVE VIDEO BUT WE MUST INCREASE THAT EFFICIENCY BY MANY FACTORS IF THEY ARE TO BE PRACTICAL. AS I SUGGESTED ( THOUGH HAVE NO IDEA OF THE OUTCOME) USING MAGNIFYING PLASTIC OVER EACH SECTION OF CELLS. THIS COULD INCREASE THAT AVAILABLE SUNLIGHT AND GIVE MORE POWER. ALSO I SUGGESTED USING NIGHT VISION TECHNOLOGY ON THE GLASS SURFACE. I ENVISION THAT IN TOTAL DARKNESS IT COULD BE AS BRIGHT AS DAY TO THOSE CELLS BUT IN SUNNY CONDITIONS WOULD BE LIKE THE SUN NEXT DOOR FOR BRIGHTNESS???!!
Good tutorial, thx
Why use only semiconductors in making a solar cell...? I mean, metals/conductors have even lesser energy gap for electrons to be free... we can get more current.. no??
The electrons are already freely moving. The principle of driving a current is potential difference. Potential difference is created due to charge separation or gradient in charge concentration.
How would you do that in metals? The charges are already separated in thermal equillibrium. You need to create a situation of charge separation as well as non equillibrium as that is the condition of flowing current.
Nice video! Does P-type generate holes and electrons under photo-excitation? Does the cell generate current with no light due to dark-current and/or thermal-excitation?
Said Everything he said in my assignment. D* thanks sir.
Thamks!!
@4.27 he was saying that the silicon created hole. Where the heck does hole come from sillicon? And also he was saying the hole and electron will cancel each other but on this circumstance the hole and electron don't cancel. What a confusion.
The hole is not a real hole. It is the absence of the electron that broke free, when hit by a photon, from its place in the atom.
Think of it like a table (the atom's nucleus) with chairs (electron bands / "trajectories" inside the atom, sorry I am not good with English) and people sitting on the chairs (electrons).
As long as the people sit on the chairs they cant move away from them and the table as long as they don't receive external help, because at this state / positions the total forces are already balanced out and the system is stable.
If some object hits a person (photon) with enough energy, it will throw it OFF the chair and away from the table.
This caused two things: People who are not sitting anymore (free electrons) and EMPTY CHAIRS (-> HOLES
DragonlordSVS thank you so much for explaining :D
Excellent :)
After connecting the wire, the rest electrons and holes neutralize each other, right? after neutralization of all the charges, does current flow stop?
If light is keep shining on the N-type surface, E-H pairs are going to keep being generated, creating a state of imbalance between the N-type and P-type. Current will flow as long as there is an imbalance.
Boa explicação, obrigado (Nice explanation, thank you)
I just used google translate on this... You said "I am of the illuminati." O.O
Why holes can diffuse to the N side from the P side but not electrons? What will happen if N side is illuminated?
+animesh mondal i also wonder this really
+Murat Sert does the hole have a charge..? I know the electron cannot pass through because it has an electron but I'm not quite sure about the hole. So yeah.. In with you guys.
+Murat Sert The explanation here isn't meant to give a complete picture as it focuses on diffusion current only. Diffusion works in both direction ( in fact holes are far less mobile than electron) but majority of the current comes from depletion region naming drift current. Band gap energy diagram is the best way to understand the mechanism.
+Brenda Smith holes have charge, the hypothesis used in this video may not be able to explain these questions. We need to have energy band diagram, band bending, drift-diffusion current to explain these questions.
In this video, the N side was illuminated which resulted in electron-hole pair. The hole was drifted to the P side by the electric field at the junction. If the P side is illuminated, then the exact opposite will happen, the electron will be drifted to the N side and hole will remain in the P side.
2:50 first row on the top looks a little ugly. But since it's a great explanatory vid overall, i don't really care for that detail.
Ok,i have a question,why doesn't slicon doped material run out of electrons and holes.If it constantly gives of an electron where does it get new ones.Someone,answer please. :)
Nevermind,i get it,when electrons leave phosporus-doped material,hole is also generated,and that hole can pass trought electric filed beetwen two doped materials.Basicaly it is always the same electrons that generate current.(btw sorry about my english)
but why hole can pass throught electric filed if there is the positive sheet that will not let it happen
4:13
Don't you run out of electrons on the left side eventually?
steveq34 why or how should that happen? (i.e. at what point: when you generate the free electron or when the electron moves through the wire or...?)
Yes and no.
There is a maximum amount of free electrons and holes that... YOU CAN HAVE AT A SINGLE TIME. This depends on the excess energy that you give to the system with the absolute maximum being the total number of electrons existing in the material (though if you break them all free what you ll have at your hands wont be a solid anymore I think, I am not a physicist or anything like it though so take what I write with a huge pinch of salt).
What matters though is that these electron and holes stay separated on either side of the semiconductor. The fact that each side has a different charge defines the voltage difference produced/existing at the illuminated semiconductor which is the only thing that matters. Remember just having free electrons and holes doesn't produce (useful) current by it self. The charges need to be somehow separated at the source and their only way to meet is via the conductor / circuit. Hence at the moment that you connect each side with a wire, free electrons from the negatively charged side "flow" through the wire towards the positively charged side of the semiconductor. This directed flow of electrons is the current. As soon as the electrons reach the positive side the atoms have their charge "rebalanced" but since we still illuminate the semiconductor they break off again becoming free electrons and holes. This continues as long as we illuminate the semiconductor.
Photons hit electrons giving them enough energy to break free off Si atoms, producing free electrons and holes, proceeding to be separated to either side of the semiconductor (hence the atoms have imbalanced and opposite charges in either side and nature hates imbalances. systems will fall to the lowest energy state because that's where they are stable), with the only way (mostly) for the free electrons to return to their missing places (holes) being through a conductor (eg wire) connecting the two sides of the semiconductor holding each, only to break free again soon after because of photons keep giving excess energy to the system (as long as it remains illuminated) and the circle "never" ends.
Excuse my crappy English btw.
Hello could you try this software? research androidcircuitsolver on google
looks confusion not coduition
ooooh