Let say we have a contact of an electron conductor and a hole conductor. How is it possible to prevent recombination of the carriers nearly completely? So, electrons do not suppose to fly or tunnel inside a hole conductor and contra, even if electric potential is applied? Could heterojunctions fit to this purpose?
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$\begingroup$ Detailed balance holds in equilibrium, so it’s kind of hard barring a depletion region between them. $\endgroup$– Jon CusterCommented Mar 23, 2019 at 23:01
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$\begingroup$ Could you explain it in a more detailed way? $\endgroup$– John SmithCommented Mar 23, 2019 at 23:09
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$\begingroup$ If $np > n_{i}^{2}$ there will be recombination. Period. $\endgroup$– Jon CusterCommented Mar 23, 2019 at 23:12
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Imagine having an electric bias (a uniform electric field) across the junction. Electrons appearing will be biased in one direction and the corresponding holes will be biased in the opposite direction. If this can be upheld until they are far enough apart, then recombination will not occur.
This is one of the key working principles of a typical solar cell, where dissimilar materials with dissimilar electron concentrations will get a natural electric field build up in this way due to electron diffusion from one to the other when in contact.
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$\begingroup$ If I understand it correctly, in solar cell the main intent is to delay the carriers recombination, not to prevent it completely. A solar cell would be useless if there wouldn't be any recombination. But in my case the task is to prevent recombination completely for indefinite period of time. $\endgroup$ Commented Mar 24, 2019 at 0:48
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1$\begingroup$ @JohnSmith The main (and only useful) recombination in a solar cell is at the metal wire connections. If you omit those, it doesn't produce useful current. $\endgroup$– Whit3rdCommented Mar 24, 2019 at 5:38
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$\begingroup$ @JohnSmith Sure, you need the recombination again, but not before the electron has travelled through the external circuit. $\endgroup$– SteevenCommented Mar 24, 2019 at 7:54