Yes, is that not the case?
By your logic all solar panels would run out of these holes after a certain period of use?
PatFussy@lemm.ee 6 months ago
wahming@monyet.cc 6 months ago
No, definitely not. There’s no such lifetime limit.
PatFussy@lemm.ee 6 months ago
Why not? I have not looked at this in forever so im probably wrong but I thought that these pn pairs end up creating some band gap. Over time that band gap widens until the energy from the sunlight just isnt strong enough to move through the system. In the end, it has a finite qty of holes so that limit depends on the qty of doped materials.
Again i dont remember well so 🤷
naevaTheRat@lemmy.dbzer0.com 6 months ago
You’re a bit jumbled up here.
There are P N junctions where the magic happens. The P side conducts by moving vacant electron “slots” through the structure, we call these holes as in electron holes. There isn’t a lack of electrons or anything, both N and P are charge neutral, instead: Where in a metal if you push an electron into it in a circuit it bumps another one over a bit and so on in a P type you pull an electron off one end, the “hole” moves taking an electron from deeper in to fill where it was until at the end it pulls another in.
As you can see the number of holes is constant under normal circumstances. We pay attention to them for reasons that’ll become clear.
Now since N types want to volunteer electrons and P types have little electron holes ready, and these are negatively and positively charged (remember overall the material is neutral though) if we put them together then in a very narrow region some holes will accept electrons and fill up. As this happens ion cores (nuclei of the atoms making up the material missing an electron) are exposed in the N type making a small positive region, while the extra electrons in the P type make a small negative region. This balances the hole-electron attraction exactly and we have a stable charge depleted region.
Following? let’s talk about lightning for a moment.
you know how everything becomes a conductor if you try hard enough? think lightning jumping down through air, a tree, and some literal earth. Well lighting ionises (pulls electrons off making a kind of gas made of charged particles) stuff mostly but there’s a special sort of state most metals and similar can get to (indeed most metals are in this state at room temperature) where they’re sort of lightly ionised. Instead of the electron going away it sort of becomes promiscuous and is happy to share its time with nearby atoms.
Electrons in this state have certain energy levels associated with them, we call this band of states the conduction band. To get to that energy state you need to go from the valence band across a "band gap " to be promoted to slutty electron.
OK so these bound hole-electron pairs moved from the conduction band to the valence band when they settled down with each other. They can’t conduct anymore. But if a photon hits them just right they trial an open marriage and separate into the conduction band. The electron is now more attracted to the positively charged region back from whence it came and visa versa for the hole. Once they get bumped over they have to go the long way round the circuit to find each other again and that’s how we get energy.
herrvogel@lemmy.world 6 months ago
They might be right for other reasons though. I once worked at a lab where they were doing r&d on this sort of thin solar cells, and their stability and longevity was the #1 biggest problem. They worked great inside those anaerobic box thingies in the lab, but they degraded to nothing very quickly upon first contact with real atmosphere.
wahming@monyet.cc 6 months ago
Yeah but that’s experimental tech. OP’s talking about limitations on normal solar panels
PatFussy@lemm.ee 6 months ago
Im talking about limitations of thin solar cells largely. I think there is usually enough doped material in regular cells that it usually isnt looked at.