Thank you for the eli5 on how PN junctions and band gap works.
All I was saying was if there is some N-type material with only some finite number of excess electrons and some P-type with finite number of holes, there is a specific energy level that this semiconductor requires for valence band conduction. The electrons are not being replaced in the circuit so the N-type is slowly losing degrading. In a normal scenario, these materials would take forever to deplete and so it is usually treated like an infinite well. In reality, a cell will have only a finite potential energy and a discrete so in effect widens the band gap until the cell is no longer functional.
On the contrary, i know thin film solar cells exist. Way back in college i remember making organic dye sensitized solar cells and they were complete garbage. I might be associating all thin cells the same way but yeah. Was a bit of time ago for me and im going off my shitty memory
naevaTheRat@lemmy.dbzer0.com 9 months ago
The electrons are being replaced, otherwise the system would become charged over time. They go the long way round the P side of the junction and bond with a hole again in the depleted region.
Solar cells do deteriorate over time but it’s not due to use, or not directly. The structure of various parts gets damaged through lattice migration due to heat/thermal cycling, UV radiation and higher can cause excitation to reactive states that damage crap, dopants can migrate around over time (like how carbon can leech from steel) and reduce the conductive efficiency etc.
I think this might be what you’re confused by? there are a finite number of available charge carriers in the depletion region and damage to the region uses them up, but it’s not because they’re used up it’s because of structural and chemical changes caused by damage that occurs due to the environment.
PatFussy@lemm.ee 9 months ago
Are they being replaced? I dont remember these circuits being closed loop. I also dont remember if photons do anything other than create a wave excitation to move electrons… where is the replenishment coming from?
I understand phonons deteriorate lattice structures. I dont know if that is a seperate issue though.
naevaTheRat@lemmy.dbzer0.com 9 months ago
So on the arse ends of the junction are little wires (one transparent). If you leave the panel in an open circuit the carriers will separate till the charge build up overcomes the depletion zone field and no more charge separation happens during excitation.
In this configuration the cell is essentially a capacitor.
If you close the circuit the P side of the electric field will propagate through the circuit and the load, pushing charge carriers through the load, out the other end, and into the P side of the junction where they combine with the separated holes.
PatFussy@lemm.ee 9 months ago
Electrons have to come from somewhere. They arent coming from sunlight. Im not understanding how even if its closed loop it will carry charge back so there is no defecit in charge. This is why i keep saying it makes sense as long as there is an assumption of infinite electrons. If you take that away, where does the potential come from…