OLED (except for phosphorescent OLED) has low internal quantum efficiency (IQE) because only 25% of electrons in the spin singlet state can emit lights, while the remaining 75% triplet electrons only produce waste heat. However, conventional LED made of GaN operate at the IQE of 80%, which is much higher than 25%. Is it because conventional LED produce higher proportion of singlets, or they can emit light via triplets as well?
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1$\begingroup$ Because any electron in the conduction band can recombine with the holes in the valence band - conventional LED works in a completely different way. $\endgroup$– Jon CusterCommented Oct 6, 2021 at 14:24
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2$\begingroup$ @JonCuster That seems like an answer, not a comment. $\endgroup$– rob ♦Commented Oct 6, 2021 at 15:39
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1 Answer
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In LED electron recombine with holes as mentioned by Jon Custer. It can go to the photon energy. The problem appears when electron recombines with the hole and the energy is given to another particle, for example another electron or hole. So this is a process limiting efficiency in LED. This process called Auger recombination.
It is a crystal process, taking into account electron and hole dispersion. Instead of a molecule process as you have, as far as I understand, in OLED.
You could read those articles: https://doi.org/10.1103/PhysRevLett.110.177406 and https://doi.org/10.1002/pssa.201431868
