5 ms·

Can someone decode/ELI5 please? (or did i just miss the joke...)

im3w1l 6y ago
It is not >100% efficient in the energy sense. But it does create more than one electron of current* per incoming photon. * Since current is charge per time, technically it creates more than one electron per second of current per incoming photon per second.
- m4r35n357 6y ago
  Yes, bad PysOrg, (or bad physicists), not to point this out!
m_j_g 6y ago
"The external quantum efficiency of a device is 100% when one incoming photon generates one electron to the external circuit. 130% efficiency means that one incoming photon generates approximately 1.3 electrons."
nybble41 6y ago
They made a detector that can convert one photon into more than one electron (about 1.3 electrons per photon on average). Note that this is not energy efficiency as in the 2nd Law of Thermodynamics; they haven't created a system that generates more energy out than it receives. The electrons have lower energy than the original photons. This "efficiency" is purely about the number of particles involved. More electrons per photon means more accurate detection of low amounts of light and also lower power requirements for light sensors in general. That would include, for example, the cells that make up a digital camera's sensor grid. Economics permitting, this could lead to better low-light performance or more efficient optical equipment (e.g. fiber optic transceivers).
- sreekotay 6y ago
  THANKS! This one stuck/made sense :)
- pier25 6y ago
  Would this also help with solar panels?
- Ductapemaster 6y ago
  Is it also a relative improvement of the energy conversion into electricity vs. into heat? Intuitively the photons energy will be partially converted into both (conservation of energy) and this efficiency improvement seems like it would skew that ratio into favor of electricity generation.
  - nybble41 6y ago
    > Is it also a relative improvement of the energy conversion into electricity vs. into heat? I would think so, since the reason the efficiency was less than 100% before was that some of the electrons were being recaptured rather than emitted from the detector. On the other hand, the article didn't say anything about the amount of energy captured. It could be that more of the photon's energy is converted into heat, with the remainder being spread across more electrons.
    - Ductapemaster 6y ago
      Ah, that's a good point. I wasn't thinking about the relative energies of the electrons themselves.
m3kw9 6y ago
Another way of saying they can generate more energy from a single photon
- ebg13 6y ago
  They say more electrons, not more energy.
- SAI_Peregrinus 6y ago
  No, same (or less) energy, more electrons. Splitting the same energy into more electrons is useful for detectors, since it increases their sensitivity.
compumike 6y ago
Normal p-n junctions (including solar panels and ordinary semiconductors) are light sensitive because one photon of light can strike and transfer its energy into creating one electron-hole pair (promoting one electron from the valence band to conduction band). This is called "optical generation", in contrast to "thermal generation". These electron-hole pairs are generated in the depletion region of the junction where they are quickly swept across by strong electric fields that arise from the junction itself. But in general, one photon = one electron-hole pair -- at most. Avalanche photodiodes already exist and convert a single incident photon into multiple charge carriers. They do this using an externally-applied electric field. This externally-applied electric field enables "impact ionization" which means that one mobile charge carrier seems to be able to knock another one loose. (As a thought experiment: imagine a bed of pebbles. Toss in another pebble, and it's likely to kick one of the existing pebbles free. Now, pretend the bed of pebbles is at a 45-degree angle to gravity. Toss a pebble in and it's more likely that the ejected pebble will itself kick another pebble loose when it lands. Make the angle steep enough and you get an "avalanche", hence the name.) As far as I can tell, the novelty here is that the high electric field is created by the geometry and materials at the surface of the nanoscale needle structure, so some version of the avalanche effect happens without needing to apply an external electric field. In the headline, efficiency refers to quantum efficiency (electrons per photon); conservation of energy still applies.
- sreekotay 6y ago
  Not quite ELI5 -- buttttt nice analogy - and I see. Particles not energy > 100% Thanks!
- news_to_me 6y ago
  Great explanation — although only a week or so ago I wouldn't have understood a lot of it. Knowing how transistors work helps a lot: https://www.youtube.com/watch?v=DXvAlwMAxiA https://www.youtube.com/watch?v=DXvAlwMAxiA
- Natsu 6y ago
  Pebbles are hard for me to imagine, instead I think of those coin games at the carnivals where you'd put in one going and a pusher device would then push things off the edge (if you were lucky).
rriepe 6y ago
If you throw an apple at an orange tree, you can knock down an orange. Someone did even better and figured out how to get two oranges to fall about 3/10 of the time.
- Judgmentality 6y ago
  I feel like this is the only actual ELI5 answer so far.

It is not >100% efficient in the energy sense. But it does create more than one electron of current* per incoming photon. * Since current is charge per time, technically it creates more than one electron per second of current per incoming photon per second.

m4r35n357 6y ago
Yes, bad PysOrg, (or bad physicists), not to point this out!

m_j_g 6y ago

"The external quantum efficiency of a device is 100% when one incoming photon generates one electron to the external circuit. 130% efficiency means that one incoming photon generates approximately 1.3 electrons."

nybble41 6y ago

They made a detector that can convert one photon into more than one electron (about 1.3 electrons per photon on average). Note that this is not energy efficiency as in the 2nd Law of Thermodynamics; they haven't created a system that generates more energy out than it receives. The electrons have lower energy than the original photons. This "efficiency" is purely about the number of particles involved. More electrons per photon means more accurate detection of low amounts of light and also lower power requirements for light sensors in general. That would include, for example, the cells that make up a digital camera's sensor grid. Economics permitting, this could lead to better low-light performance or more efficient optical equipment (e.g. fiber optic transceivers).

sreekotay 6y ago
THANKS! This one stuck/made sense :)
pier25 6y ago
Would this also help with solar panels?
Ductapemaster 6y ago
Is it also a relative improvement of the energy conversion into electricity vs. into heat? Intuitively the photons energy will be partially converted into both (conservation of energy) and this efficiency improvement seems like it would skew that ratio into favor of electricity generation.
- nybble41 6y ago
  > Is it also a relative improvement of the energy conversion into electricity vs. into heat? I would think so, since the reason the efficiency was less than 100% before was that some of the electrons were being recaptured rather than emitted from the detector. On the other hand, the article didn't say anything about the amount of energy captured. It could be that more of the photon's energy is converted into heat, with the remainder being spread across more electrons.
  - Ductapemaster 6y ago
    Ah, that's a good point. I wasn't thinking about the relative energies of the electrons themselves.

m3kw9 6y ago

Another way of saying they can generate more energy from a single photon

ebg13 6y ago
They say more electrons, not more energy.
SAI_Peregrinus 6y ago
No, same (or less) energy, more electrons. Splitting the same energy into more electrons is useful for detectors, since it increases their sensitivity.

compumike 6y ago

Normal p-n junctions (including solar panels and ordinary semiconductors) are light sensitive because one photon of light can strike and transfer its energy into creating one electron-hole pair (promoting one electron from the valence band to conduction band). This is called "optical generation", in contrast to "thermal generation". These electron-hole pairs are generated in the depletion region of the junction where they are quickly swept across by strong electric fields that arise from the junction itself. But in general, one photon = one electron-hole pair -- at most. Avalanche photodiodes already exist and convert a single incident photon into multiple charge carriers. They do this using an externally-applied electric field. This externally-applied electric field enables "impact ionization" which means that one mobile charge carrier seems to be able to knock another one loose. (As a thought experiment: imagine a bed of pebbles. Toss in another pebble, and it's likely to kick one of the existing pebbles free. Now, pretend the bed of pebbles is at a 45-degree angle to gravity. Toss a pebble in and it's more likely that the ejected pebble will itself kick another pebble loose when it lands. Make the angle steep enough and you get an "avalanche", hence the name.) As far as I can tell, the novelty here is that the high electric field is created by the geometry and materials at the surface of the nanoscale needle structure, so some version of the avalanche effect happens without needing to apply an external electric field. In the headline, efficiency refers to quantum efficiency (electrons per photon); conservation of energy still applies.

sreekotay 6y ago
Not quite ELI5 -- buttttt nice analogy - and I see. Particles not energy > 100% Thanks!
news_to_me 6y ago
Great explanation — although only a week or so ago I wouldn't have understood a lot of it. Knowing how transistors work helps a lot: https://www.youtube.com/watch?v=DXvAlwMAxiA https://www.youtube.com/watch?v=DXvAlwMAxiA
Natsu 6y ago
Pebbles are hard for me to imagine, instead I think of those coin games at the carnivals where you'd put in one going and a pusher device would then push things off the edge (if you were lucky).

rriepe 6y ago

If you throw an apple at an orange tree, you can knock down an orange. Someone did even better and figured out how to get two oranges to fall about 3/10 of the time.

Judgmentality 6y ago
I feel like this is the only actual ELI5 answer so far.