The Weird, Weird Quantum Physics of Solar Panels (And Everything Else)
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- Опубліковано 12 чер 2024
- In this video we talk about the weird quantum physics of photovoltaics including band theory, the Fermi sea, carrier lifetimes and recombination (and school buses!)
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Technical Caveat: It is common practice when drawing energy band diagrams between two different materials to draw them such that the electron filling level (i.e. Fermi level) is constant from material to material. However, here we take the approach of effectively having a flat vacuum level and allowing the Fermi level to spatially vary. These two approaches are ultimately equivalent but this way has the advantage of not having to discuss issues like the physical meaning of the electrochemical potential and discussing where and why the Fermi level actually rests in a doped semiconductor. - Наука та технологія
"There is no analogy to the Pauli exclusion principle in the non-quantum world" ..... then gives a perfect schoolbus analogy. ;-)
THAT's how you teach physics!
Thank you, sir.
HE'S BACK. Another great video! Love it.
The video of the limitations would be awesome, it's hard to find information about the topic on the internet
I have just discovered your channel - Stopping & starting enables the concepts to be understood - My understanding is consolidated when I explain it to my grandson so he can understand - WELL DONE - KEEP UP THE GOOD WORK
I've watched several videos that cover the bands, but something about they way you presented it helped me finally understand it better. Overall a very interesting video and I would definitely be interested in a follow up about the limitations.
Great video!! But I wonder why it isn't reaching a wider audience! If ya ever want to work together, reach out!
Finally I understand band-gap and all that! Years of scratching my head ... Thanks!
Amazing video!! This made me finally understand why electrons don't just always jump to the lowest energy state. Great explanation of a surprisingly interesting topic, hope more people find this channel
man you're heavily underrated
This is so informative. This is fourth video on the channel I am watching rn. I might watch all of them.
Like an electron I am excited :)
Really great didactic style. Something seemingly complex gets ever more graspable with every video of yours.
I watch these videos when I need a break from my biology studies.
Any videos on the quantum physics of biochemical/biomechanical processes would definitely be very appreciated by me:)
Like maybe start with a basic one of why ATP/ADP (and all the others tri-/di--phosphate types of biochemistry) has been "elected" by evolution as the molecule of choice for delivering energy to enzymes and proteins. What makes them so great compared to other possible energy carriers?
More generally. How or in what ways has evolution been optimizing within the search-space of quantum-mechanical properties? Is there any correlation between evolutions "choice" of chemistry and quantum mechanics? (I'd assume there is.. evolution has quite the history of optimizing over time in every possible manner)
Anyways, great great stuff! Based on the comments, it seems that many of us are grateful. I surely am.
Great video! will be waiting on that video on limit of solar cell efficiency
This channel needs to be way higher. Very good quality content!
All of your videos so far have been my go-to when I have to explain something like this to normies. More completely detailed than most (until you get into lecture territory) and still super easy to understand such as the term or visual "down hill" instead of potential energy to make the same point. Keep on keeping on Spork. Great stuff.
I would like to see a video on the limitations. I heard that when a photon has more than the band gap energy, the extra energy is lost, but when it has less than the band gap, it does not create an electron-hole pair. So with a wide spectrum source (sunlight), there is a trade off between voltage and photocurrent. But I am sure that is only half the story.
Great video! I really like your style of presentation and would love a follow-up on modern organic PV cells!
Your videos are part of youtube that is not crap. Make one more please
Please don't stop uploading 🙏🙏
this is brilliant! Could you possibly make a similar video explaining how LEDs work? Since the demise of the filament bulb, we now all use LED bulbs but view of us know clearly how they work.
An suggestion for alternative title for more reach - An amazing physics of solar panel.
Excellent excellent exposition of the complex subject
Still waiting for your next video on condensed matter physics. Please bring the next video. We are eager to learn more.
Hi, Great explanation.
I watched most of your videos and found them great as explaining physics intuitively, but more important, causally.
Meaning, they explain how certain phenomena are created by the rules of lower-level phenomena (Like how you explained magnetic force using retarded electric force in your first video).
I want to challenge you to explain several other phenomena that I have not been able to find a causal explanation:
1) Why only certain energy levels are allowed for electrons in atoms?
We know that only wavelengths of whole Planck multiplications are allowed, but why it is so?
Can this effect perhaps be explained by other known phenomena, like the electric and magnetic forces applied on such electron that allows a stable "orbit" or path? Or do we have to take it as a fundamental postulate?
2) What is the relation between photos and EM waves. Those two descriptions of light do not seem to reconcile. Is a photon a disturbance in the EM field, and if so, how come it does not spread in all directions? Or are multiple photons are combined somehow and create the electromagnetic wave.
THE KING RETURNS
😢 I do wish your talent in popularizing science was recognized
Excellent. Thankyou 👍
Thank you!
Thanks! Think I followed OK... kinda weird indeed. I mean... how do they know that there are other electrons in the state they are trying to become? Weird... but the "mechanics" made sense at least
Sabine Hossenfelder just uploaded a video about the chaotic tumbling of Hyperion vs quantum mechanics. I am a bit dissatisfied with the explanation. Please do a video about this.
Excellent video! Thank you a million times. You must have a great understanding of quantum mechanics because your explanations are so clear. Please consider doing a video on how the Schrodinger equation is actually used in practice. I hear it predicts the location of electrons which raises questions to me. Aren’t electrons always moving? They are so small how is their location even measured?
Thanks
One example of how the Schrodinger equation is used in practice that might be easier to understand is in atomic physics. The case of the hydrogen atom is analytically solvable, and is done in many textbooks and courses. For atoms with multiple electrons, it is more complicated, and people have developed a lot of ways to approximate the solution to the many-electron problem, but these typically rely on numerical methods. You can look up Hartree-Fock, density functional theory, and coupled cluster for examples of such methods, although they will be difficult to understand if you don't have much background in quantum mechanics.
Back to the hydrogen atom, the Schrodinger equation for the electron in the hydrogen atom consists of two terms: one for the kinetic energy of the electron and one for the potential energy of the electron. The kinetic energy term is related to the Laplacian of the electron wave function, and the potential energy is related to the 1/r potential from the potential of the proton (which is treated as a point charge). "Solving the Schrodinger equation" means finding wave functions, usually denoted with the Greek letter psi, that solve the partial differential equation given by the Schrodinger equation. Typically, one solves the time-independent Schrodinger equation since the solution of the time-independent Schrodinger equation gives you the information that you typically want, and time-evoluation is straight forward once you solve the time-independent Schrodinger equation. The form of the time-independent Schrodinger equation is that of an eigenvalue problem, just like in linear algebra. In linear algebra, a matrix A can have eigenvalues a and eigenvectors V such that A*V = a*V, and a common task is to find the a and V. In the time-independent Schrodinger equation, you have H*psi = E*psi is the eigenvalue problem that you are trying to solve, and it takes the form of a differential equation. H is equal to the kinetic energy + potential energy terms in the simplest case (it can get more complicated than that, but it's not important for now). So, when one talks about "solving the Schrodinger equation" that refers to finding the eigenvalues, E, and eigenvectors, psi, of the differential equation given by H. For each system, whether it's a particle in a box, a particle in a harmonic potential, or a hydrogen atom, the differential equation given by H will be different. The quantities that you solve for, E and psi, have direct physical interpretations (I think that what their interpretations are are the crux of your questions). The values for E that you find yield solutions to the Schrodinger equation give you the possible energy states that your electron can be in. It's similar to how in the video it's mentioned that in a semiconductor there's an energy region where no electron states are available: in the Schrodinger equation, one would see that there aren't energy values E in that range that allow the differential equation to be solved. Just like in the case of eigenvalues and eigenvectors in a matrix, the energies that you find, E, have associated wave functions, psi, that tell you what that given energy state looks like. You can look up the wave functions of the hydrogen atom, and you'll see for instance that the 1s wave function looks different from the 2s and 3s wave functions, for example. The wave function is a function defined as a function of x, y, and z (or in spherical r, theta, and phi) that you can manipulate to find what is the probability amplitude for finding an electron in a given region of space. You can also use it to answer questions like "what is the average distance of an electron in the 2s state of the hydrogen atom from the proton?"
Another interesting question that you can ask might be something like "what will happen if I apply an electric field to a hydrogen atom?" To answer this question, you have to take into account the potential generated by your external electric field. This will modify the potential energy term in the Schrodinger equation, and give you a new set of possible energy values, E, and associated wave functions, psi, that solve the new Schrodinger equation. In fact, if the electric field is small in magnitude, then you can use your knowledge of the energies and wave functions from the hydrogen atom to find our how a small electric field will change the allowed energies and wave functions of your electron. This is called "perturbation theory" which is a very important part of quantum mechanics since it allows you to take advantage of your knowledge of problems like the hydrogen atom which can be solved exactly.
So, in summary, the Schrodinger equation incorporates information about your specific physical system via writing down the kinetic and potential energies of the particles in your system. Once you've done that, you end up with a partial differential equation that can be solved to yield the allowed energy values in your system, and also the associated wave functions (which are related to probability densities of the particle positions). Knowledge of the allowed energies and their wave functions gives you the ability to compute a lot of different properties of your system. For example, in a molecule or solid you can develop approximations for the Schrodinger equation that allow you to compute the vibrational frequencies of the atoms (which can be related to things like IR or Raman spectra), binding energies of components of the molecule to each other (which can be compared with experimental formation enthalpy values), and the allowed energy levels which you can use to predict what frequencies of light the molecule or solid can absorb. The density of states that is referred to in the video can be calculated for a given material by solving an approximation for the Schrodinger equation.
@@AlexSmith-ox6dl Thank you!
how to objects stay the same colour - if the frequency of the re-emitted photon is dependent on the frequency of the photn the electron absorbed, how does an atom continuously produce a photon of the same colour/ why is an atoms colour constant?
Another thought I had is that much of the inefficiency of solar panels must be due to the intraband relaxation, so the number of bands above the electrons above the band gap is probably positively correlated to the inefficiency of the solar panel. Does that mean that solar panels are more efficient with light that has smaller wavelengths? The higher wavelengths would put the electrons higher up above the band gap, which would give them more opportunities to lose some of their energy via intraband relaxations, right? Or is my assumption that only the outermost electrons get excited wrong?
Correct and you can indeed look up that silicon solar panels are most efficient in red to infrared wavelengths! It's not that only the outermost electrons get excited but even when an electron from lower down gets excited (by let's say UV photon), others from that band quickly fill it's place so the "hole" looses energy as well.
Well in a follow up video I would discuss the ultimate trade-off in band gap vs. intra-band relaxation that is called the "Shockley-Quiessar limit" which you might want to have a look at. You also might want to also have a look at the concept behind a "tandem" cell which tries to circumvent these issues by stacking multiple PN junctions of different materials with different band gaps in order to more fully capture the energy range of sunlight.
@@atomsandsporks6760 off topic, but I have a question to ask. I have done masters in physics but my specialization wasnt in condensed matter. So I have ideas of "solid state physics" taught in the undergraduate level and a little bit of masters level things taught in generalized course like tight binding approx, nearly free e- approx, and preliminary idea about superconductivity, bcs theory, but no idea on stuff like fock theory, kondo effect,HF theory etc as it was not my specialization.
But if I were to really learn those materials at a masters/grad school level, what book/lectures and material should I follow, in say 4-5 months of time? What should be my strategy?
It will be really beneficial to know that. Thank you, enjoying your videos a lot.
What software do you use to make it?
Why haven't you posted in so long (1 year)
Sir🌟🌟🌟what is the difference between detection and measurement.... in Quantum mechanics?
Why detection does not collapse wave function but MEASUREMENT DOES ??
THANK YOU SIR 🌟
So..... metals are like fluorescent materials because their electrons drop down super fast, and semiconductors are like phosphorescent materials because their electrons drop down more slowly. And a solar pannel is like a phosphorescent material in which the excited electrons were carried away by an electric field (into wires) before they were able to drop down? So would it be possible to make an actual solar pannel from a phosphorescent material?
How exactly do fluorescent and phosphorescent materials fit into all of this? am I taking the analogy way too far? or are they like exactly the same thing so it's not really an analogy but just a different instance of the same phenomenon?
and also, are ALL materials fluorescent/phosphorescent, it's just that only some materials do it at the visible wavelengths? People often talk about fluorescence/phosphorescence as if it were a qalitatively very different property of a material, but I've always wondered if we just couldn't see that all/most materials do it.
So clearly, I would love a video that goes into detail on fluorescence/phosphorescence. I NEED that video!
There is something called a dye-sensitized solar cell that you might want to look into that takes some of these ideas. But simply having a phosphorescent material by itself is missing the junction aspect, which is crucial. Without the PN junction, if you just had a slab of semiconductor, then electrons would excite, be "held up" by inter-band relaxation being slow, but then eventually relax regardless because there's no mechanism pushing them anywhere.
No more videos... still there?
Hey I love your content where are you?
If the "electron particle" model cannot describe a basic capacitor properly, i.e. the dissectible capacitor experiment contradicts electron theory's prediction, then why do we think the "electron particle" model will properly describe the semi-conductor behavior? Semi-conductors are just a specific form of capacitor, i.e. metals and dielectric "insulator".
The idea that Quantum Physics is its own "specific/specialized physics that is confusing" is BASED upon an incorrect electron particle theory... of course, that would lead to more confusion.
Don't you think the fact that quantum physics cannot explain how a common object operates without calling it "weird" is strong evidence that quantum physics is wrong?